Clinical Vignettes for the USMLE Step 1 PreTest Self-Assessment and Review, Fourth Edition (PreTest Basic Science)

Clinical Vignettes for the USMLE Step 1 TM

PreTest Self-Assessment and Review

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Clinical Vignettes for the USMLE Step 1 TM

PreTest Self-Assessment and Review Fourth Edition

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Questions Block 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Block 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Block 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Block 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Block 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Block 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Block 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Answers Block 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Block 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Block 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 Block 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 Block 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 Block 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 Block 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

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Introduction The current format of the United States Medical Licensing Examination Step 1 (USMLE Step 1) exam emphasizes clinical vignettes—in single-bestanswer multiple-choice format—as the only test question. The examination is 350 questions broken into seven blocks of 50 questions each. Examinees have one hour to complete each block. Clinical Vignettes for the USMLE Step 1: Fourth Edition parallels this format. The book contains 350 clinical vignette-style questions covering the core basic sciences and was assembled based on the published content outline for the USMLE Step 1. The questions are divided into 7 blocks of 50 questions. As on the Step 1 exam, each block tests the examinee on all core basic science areas. Answers are in the second half of the book. Each answer is accompanied by a concise but comprehensive explanation and is referenced to a key textbook or journal article for further reading. The questions in this book were culled from the seven PreTest Basic Science books. The publisher acknowledges and thanks the following authors for their contributions to this book: Anatomy, Histology, and Cell Biology: Robert M. Klein, PhD and George C. Enders, PhD Biochemistry and Genetics: Golder Wilson, MD Microbiology: James D. Kettering, PhD and Hansel M. Fletcher, PhD Neuroscience: Allan Siegel, PhD Pathology: Earl J. Brown, MD Pharmacology: Marshal Shlafer, PhD Physiology: Patricia Metting, PhD McGraw-Hill November 2007

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Block 1 Questions 1-1. A patient has been referred to your academic medical center because of recent-onset ventricular ectopy, second degree AV nodal block, chromatopsia, and other extracardiac signs and symptoms of digoxin intoxication. His family doctor, who has been treating him for a host of common medical problems over the last 30 years, had prescribed furosemide and digoxin for this gentleman’s heart failure. Blood tests show that serum digoxin levels are well within a normal range. We believe the problems are diureticinduced. Which of the following does the diuretic most likely do to account for the digoxin toxicity? a. b. c. d. e.

Caused hypercalcemia Caused hypokalemia Caused hyponatremia Displaced digoxin from tissue binding sites Inhibited digoxin’s metabolic elimination

1-2. A 62-year-old male who was diagnosed with lung cancer also displays weakness in his arms and legs. A battery of tests are administered to the patient, including those involving nerve conduction. The nerve conduction test reveals a reduction in the compound motor action potential relating to muscles of the hand. However, the amplitude of this potential improves significantly following exercise involving the relevant muscles. Which of the following is the most likely diagnosis? a. b. c. d. e.

MS ALS Myasthenia gravis Lambert-Eaton syndrome MD

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Clinical Vignettes for the USMLE Step 1

1-3. A 29-year-old woman (gravida 3, para 2) gave birth to a healthy baby after 38 weeks of gestation and delivered the intact placenta spontaneously. The pregnancy was complicated by preeclampsia, but fetal monitoring and ultrasound were normal throughout gestation. The predominant structures shown in the accompanying photomicrograph of the placenta are derived from which of the following?

a. b. c. d. e.

A combination of fetal and maternal tissues Endometrial glands Endometrial stroma Fetal tissues Maternal blood vessels

1-4. A 48-year old woman suffering from a severe tension headache is brought to the Emergency Department after her husband discovered her unresponsive and barely breathing when he stopped at home from work during his lunch hour. A bottle of Vicodin was found next to the bathroom sink. Which of the following arterial blood gases are most consistent with her clinical presentation? a. pH = 7.27; PaCO2 = 60 mmHg, [HCO3–] = 26 mEq/L, Anion Gap = 12 mEq/L b. pH = 7.02; PaCO2 = 60 mmHg, [HCO3–] = 15 mEq/L, Anion Gap = 12 mEq/L

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c. pH = 7.10; PaCO2 = 20 mmHg, [HCO3–] = 6 mEq/L, Anion Gap = 30 mEq/L d. pH = 7.51; PaCO2 = 49 mmHg, [HCO3–] = 38 mEq/L, Anion Gap = 14 mEq/L e. pH = 7.40; PaCO2 = 20 mmHg, [HCO3–] = 10 mEq/L, Anion Gap = 26 mEq/L

1-5. A 6-month old infant is admitted to the hospital with acute meningitis. The Gram stain reveals gram-positive, short rods, and the mother indicates that the child has received “all” of the meningitis vaccinations. Which of the following is the most likely cause of the disease? a. b. c. d. e.

H. influenzae L. monocytogenes N. meningitidis, group A N. meningitidis, group C S. pneumoniae

1-6. An AIDS patient complains of headaches and disorientation. A clinical diagnosis of Toxoplasma encephalitis is made, and Toxoplasma cysts are observed in a brain section (see figure below). Which of the following antibody results would be most likely in this patient?

a. b. c. d. e.

IgM nonreactive, IgG nonreactive IgM nonreactive, IgG reactive (low titer) IgM reactive (low titer), IgG reactive (high titer) IgM reactive (high titer), IgG reactive (high titer) IgM reactive (high titer), IgG nonreactive

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Clinical Vignettes for the USMLE Step 1

1-7. A 14-month-old boy presents with a fever of 102°F. The child has a longstanding history of recurrent lower respiratory tract infections including bronchitis and pneumonia. Chronic diarrhea is a longstanding problem. His mother reports that she had numerous upper respiratory infections and chronic diarrhea as a young child. A complete blood count, lung function tests, and urinalysis values are all within normal range. Serum immunoglobulin levels are normal for IgG and IgM, but IgA was 25 mg/dL (normal = 40–60 mg/dL). There are numerous neutrophils and other white cells in the stool sample and the stool is cultured for specific bacteria. IgA coats pathogens facilitating repulsion of the negative charge on the cell membrane. That negative charge on the cell membrane is primarily caused by which of the following? a. b. c. d. e.

Free saccharide groups Glycoprotein Cholesterol Peripheral membrane protein Integrins

1-8. A 47-year-old man presents with headaches, muscle weakness, and leg cramps. He is not currently taking any medications. Physical examination finds a thin adult man with mild hypertension. Laboratory examination reveals slightly increased sodium, decreased serum potassium level, and decreased hydrogen ion concentration. Serum glucose levels are within normal limits. A CT scan reveals a large tumor involving the cortex of his left adrenal gland. Which of the following combinations of serum laboratory findings is most likely to be present in this individual? a. b. c. d. e.

Decreased aldosterone with increased renin Decreased cortisol with decreased ACTH Increased aldosterone with decreased renin Increased cortisol with increased ACTH Increased deoxycorticosterone with increased cortisol

1-9. Following hemisection of the spinal cord at the level of approximately T3, a patient experiences loss of pain and temperature on the left side of the leg. Which of the following tracts was affected by the hemisection of the cord that could account for this deficit? a. b. c. d. e.

Right fasciculus cuneatus Right fasciculus gracilis Right spinothalamic tract Left spinothalamic tract Left corticospinal tract

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1-10. A 27-year-old patient with insulin-dependent diabetes mellitus told his roommate that he could not afford to refill his insulin prescription until he got a paycheck. The roommate offered to get it for him, but the patient assured him he could wait until after the weekend. When the roommate returned from a weekend trip on Sunday evening, he found the man unresponsive on the couch, and called 9-1-1. Which of the following arterial blood gases taken in the Emergency Department would be expected in diabetic coma? a. b. c. d. e.

pH = 7.22; PaCO2 = 60 mmHg, [HCO3–] = 26 mEq/L, Anion Gap = 12 mEq/L pH = 7.02; PaCO2 = 60 mmHg, [HCO3–] = 15 mEq/L, Anion Gap = 12 mEq/L pH = 7.10; PaCO2 = 20 mmHg, [HCO3–] = 6 mEq/L, Anion Gap = 30 mEq/L pH = 7.51; PaCO2 = 49 mmHg, [HCO3–] = 38 mEq/L, Anion Gap = 14 mEq/L pH = 7.40; PaCO2 = 20 mmHg, [HCO3–] = 10 mEq/L, Anion Gap = 26 mEq/L

1-11. A 63-year-old man presents with signs of congestive heart failure, including shortness of breath, cough, and paroxysmal nocturnal dyspnea. Physical examination reveals a hyperdynamic, bounding, “water-hammer” pulse and a decrescendo diastolic murmur. His hyperdynamic pulse causes “bobbing” of his head. Which of the following is the most frequent cause of the cardiac valvular abnormality present in this individual? a. b. c. d. e.

Aortic dissection Infective endocarditis Latent syphilis Marfan syndrome Rheumatic fever

1-12. An elderly female suffering from an infection complained that she could not salivate and was unable to display lacrimation on the right side of her face. Following a neurological examination, it was determined that a peripheral component of a cranial nerve was affected by this disorder. Which of the following cell bodies of origin form the origin of the affected cranial nerve? a. b. c. d. e.

Dorsal motor nucleus of the vagus Nucleus ambiguus Inferior salivatory nucleus Superior salivatory nucleus Edinger-Westphal nucleus of cranial nerve III

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Clinical Vignettes for the USMLE Step 1

1-13. An immunocompromised person with a history of seizures has an MRI that reveals a temporal lobe lesion. Brain biopsy results show multinucleated giant cells with intranuclear inclusions. Which of the following is the most probable cause of the lesion? a. b. c. d. e.

Coxsackievirus Hepatitis C virus Herpes simplex virus Listeria monocytogenes Parvovirus

1-14. Soon after returning from a trip to Costa Rica, a 41-year-old woman develops recurrent chills and high fever that recur every 48 h. Examination of her peripheral blood reveals red granules (Schüffner’s dots) in enlarged, young erythrocytes. Which of the following organisms is most likely to have produced her signs and symptoms? a. b. c. d. e.

Afipia felis Ancyclostoma duodenale B. microti P. ovale Toxoplasma gondii

1-15. A 22-year-old woman presents at the ophthalmology clinic. She describes an initial inability to drive at night because of what she describes as “night blindness.” She says that the deterioration of her vision has continued and she is having difficulty seeing objects on the periphery of her vision. Visual acuity, color, visual field, dark adaptation, and ERG testing is completed. The tests show rod degeneration with limited peripheral vision. She has pigment deposits in the mid-peripheral retina known as “bone spicules.” She also has attenuated vessels in the retina and paleness of the optic nerves. An electroretinogram (ERG) is reduced in amplitude. The cause may be related to a failure of opsin and other protein vesicle transport. This transport would occur along which of the following? a. b. c. d. e.

Microfilaments (thin filaments) Thick filaments Microtubules Intermediate filaments Spectrin heterodimers

1-16. A 57-year-old woman is undergoing a femoral popliteal bypass for her peripheral vascular disease. The vascular surgeon wishes to induce a localized arteriolar constriction to help control hemostasis. An increase in

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the local concentration of which of the following agents will cause systemic vasoconstriction? a. b. c. d. e.

Nitric oxide Angiotensin II Atrial natriuretic peptide A b2-adrenergic agonist Adenosine

1-17. We administer a drug with the intent of lowering a patient’s elevated LDL and total cholesterol levels, and raising HDL levels. The drug we choose inhibits cholesterol synthesis by inhibiting 3-hydroxy-3-methylglutarylcoenzyme A (better known as [HMG CoA] reductase). Which of the following drugs best fits this description and works by the stated mechanism of action? a. b. c. d. e.

Clofibrate Gemfibrozil Lovastatin Nicotinic acid (niacin) Probucol

1-18. A parent is correcting his child’s photograph for red eye and notes one of the child’s pupils reflects the flash as white rather than red. An ophthalmologist confirms the presence of a tumor in the back of the whitereflecting eye, telling the parents about the possibility of retinoblastoma (180200). The parents return to their pediatrician, confused about the relation of retinoblastoma (Rb) and B-cell lymphoma (bcl) genes they saw on the Internet and the possibility their child’s tumor is inherited. Which of the following is the most appropriate response? a. Rb and bcl proteins are polymerases that prevent oncogenesis by stringent DNA repair; the parents are therefore carriers for autosomal recessive Rb deficiency with a 1 in 4 recurrence risk. b. Rb protein binds transcription factors needed for cell division and bcl protein (cyclin D1) stimulates it; Rb is a tumor suppressor gene requiring homozygous mutations (two hits) that are likely sporadic in a child with unilateral tumor. c. Rb and bcl proteins are DNA-binding factors that suppress promoters near oncogenes and act as tumor suppressors; the child represents a new, dominantacting mutation and the parents have a minimal recurrence risk. d. Rb protein stimulates cyclins specific for retinal tissue and bcl does the same for lymphatic cyclins; the child represents a new mutation with excess Rb activity. e. Rb protein forms complexes with bcl protein that promotes cell division in rapidly proliferating tissues; the child represents a new mutation with excess Rb-bcl complex activity.

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Clinical Vignettes for the USMLE Step 1

1-19. A 48-year-old woman presents with a 1.5-cm firm mass in the upper outer quadrant of her left breast. A biopsy from this mass reveals many of the ducts to be filled with atypical cells. In the center of these ducts there is extensive necrosis. No invasion into the surrounding fibrous tissue is seen. Which of the following is the most likely diagnosis? a. b. c. d. e.

Colloid carcinoma Comedocarcinoma Infiltrating ductal carcinoma Infiltrating lobular carcinoma Lobular carcinoma in situ

1-20. A forest worker experiences a sudden onset of fever, headache, myalgias, and prostration. A macular rash develops several days later, with it appearing first on the hands and feet before moving onto his trunk. Which of the following treatments is most appropriate? a. b. c. d. e.

Amphoteracin B Cephalosporin Erythromycin Sulfonamides Tetracycline

1-21. A 29-year-old woman presents with nervousness, heat intolerance, and weight loss. Physical examination reveals the presence of exophthalmus, pretibial myxedema, and diffuse enlargement of the thyroid. Laboratory examination reveals elevated serum thyroxine (T4) and triiodothyronine (T3) levels, while the level of serum thyroid-stimulating hormone (TSH) is decreased. Histologic sections from her thyroid gland reveal increased cellularity with scalloping of the colloid at the margins of the follicles. Which of the following types of autoantibodies is most specific for this individual disease? a. b. c. d. e.

Antimicrosomal antibodies Antithyroglobulin antibodies Antithyroid peroxidase antibodies TSH-receptor-blocking antibodies TSH-receptor-stimulating antibodies

1-22. A 27-year-old woman presents with tender cervical lymphadenopathy. A biopsy of one of the enlarged lymph nodes in this area is diagnosed by the pathologist as being a “reactive lymph node with follicular hyperplasia.” The associated schematic depicts the morphology of this reactive change. The majority of the proliferating cells in the area marked by the

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arrow labeled with an “*” are in the process of transforming into cells that eventually will secrete which substance?

a. b. c. d. e.

Erythropoietin Gamma-interferon Immunoglobulin Interleukin-2 Interleukin-3

1-23. A 65-year-old man presents to the neurology clinic with a several year history in which he has less and less energy and spontaneity, memory loss (especially recent events), and mood swings. He is described by his wife as uncharacteristically slow to learn and react and shying away from anything new, preferring the familiar, confused, getting lost easily, and exercising poor judgment. He scores poorly on the mini-mental status examination (MMSE). This disease is believed to be caused by protein misfolding. Chaperonins regulate protein folding in which of the following ways? a. Stimulating aggregation of proteins b. Contributing folding information to the native protein c. Controlling the docking of the signal peptide with its receptor on the rough endoplasmic reticulum d. Inhibiting proteolytic activity of misfolded proteins e. Using their ATPase activity to bind and release themselves from hydrophobic regions of the protein

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Clinical Vignettes for the USMLE Step 1

1-24. A 17-year-old boy is admitted to the hospital with a traumatic brain injury, sustained when he fell off his motorcycle. He develops a fever of 39°C, which is unrelated to an infection or inflammation. The fever is most likely due to a lesion of which of the following? a. b. c. d. e.

The lateral hypothalamus The arcuate nucleus The posterior nucleus The paraventricular nucleus The anterior hypothalamus

1-25. A 3-year-old girl, with no history of vaccination, is brought to the hospital with a sore throat, fever, malaise, and difficulty breathing. Physical examination reveals a gray membrane covering the pharynx. Growth of the etiologic agent on cysteine-tellurite agar forms gray to black colonies with a brown halo. The major virulence factor of this organism is only produced by those strains that will most likely have which of the following characteristics? a. b. c. d. e.

Encapsulated Glucose fermenters Lysogenic for β-prophage Of the mitis strain Sucrose fermenters

1-26. A patient with epilepsy is started on oral therapy with an appropriate anticonvulsant. Not long after treatment starts he manifests psychotic behaviors that were not present before antiepileptic drug therapy started. Of the following antiepileptic agents, which is associated with the highest risk of causing psychosis? a. b. c. d. e.

Ethosuximide Phenobarbital Phenytoin Valproic acid Vigabatrin

1-27. A newborn boy is born with first arch congenital malformations classified as Treacher-Collins syndrome, which is an autosomal dominant inherited disorder. The Treacher Collins-Franceschetti syndrome 1 (TCOF) gene encodes the protein treacle. Treacle is localized to the structure labeled with the arrows in the accompanying transmission electron micrograph. Treacle is most likely involved in which of the following?

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a. b. c. d. e.

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Assembly of ribosomal subunits into mature ribosomes Translation of cytosolic proteins Transcription of nuclear proteins Transcription of ribosomal proteins Organelle degradation

1-28. A 34-year-old man with mild anxiety and depression symptoms has heard about buspirone on television and asks whether it might be suitable for him. According to the latest diagnostic criteria, the drug would be appropriate, particularly for short-term symptom control. Which of the following best describes an important property of this drug? a. Associated with a withdrawal syndrome that, if unsupervised, is frequently lethal b. Has a significant potential for abuse c. Is likely to potentiate the CNS depressant effects of alcohol, benzodiazepines, and sedative antihistamines (e.g., diphenhydramine), so such interactants must be avoided at all cost d. Requires almost daily dosage titrations in order to optimize the response e. Seldom causes drowsiness

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Clinical Vignettes for the USMLE Step 1

1-29. A 47-year-old female is brought to the Emergency Department because she fainted at the gym during her daily aerobic workout. A prominent systolic murmur is heard and a presumptive diagnosis of aortic stenosis is made. Which of the following is consistent with that diagnosis? a. b. c. d. e.

A decreased pulse pressure An increased arterial pressure A decreased left ventricular diastolic pressure An increased ejection fraction A decreased cardiac oxygen consumption

1-30. A 5-year-old Egyptian boy receives a sulfonamide antibiotic as prophylaxis for recurrent urinary tract infections. Although he was previously healthy and well-nourished, he becomes progressively ill and presents to your office with pallor and irritability. A blood count shows that he is severely anemic with jaundice due to hemolysis of red blood cells. Which of the following is the simplest test for diagnosis? a. b. c. d.

Northern blotting of red blood cell mRNA Enzyme assay of red blood cell hemolysate Western blotting of red blood cell hemolysates Amplification of red blood cell DNA and hybridization with allele-specific oligonucleotides (PCR-ASOs) e. Southern blot analysis for gene deletions

1-31. An 11-year-old boy presents with ciliary dyskinesia, sinusitis, and bronchiectasis. He has had persistent infections and otitis media since birth. A PA radiograph shows dextrocardia, and he has a negative saccharin test. In the cross-section of the cilium shown below, which of the following is primarily affected in this disorder?

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Structure A Structure B Structure C Structure D Structure E

1-32. Two weeks after contact with an individual with an acute disease presentation, a 12-year-old girl has fever and malaise, followed by a rash composed of crops of vesicles which lasts 5 days. This common childhood disease is caused by which of the following viruses? a. b. c. d. e.

Adenovirus Cytomegalovirus Papillomavirus Rubeola Varicella virus

1-33. A 2-day-old neonate becomes lethargic and uninterested in breastfeeding. Physical examination reveals hypotonia (low muscle tone), muscle twitching that suggests seizures, and tachypnea (rapid breathing). The child has a normal heartbeat and breath sounds with no indication of cardiorespiratory disease. Initial blood chemistry values include normal glucose, sodium, potassium, chloride, and bicarbonate (HCO3–) levels; initial blood gas values reveal a pH of 7.53, partial pressure of oxygen (Po2) normal at 103 mmHg, and partial pressure of carbon dioxide (Pco2) decreased at 27 mmHg. Which of the following treatment strategies is most appropriate? a. b. c. d. e.

Administer alkali to treat metabolic acidosis Administer alkali to treat respiratory acidosis Decrease the respiratory rate to treat metabolic acidosis Decrease the respiratory rate to treat respiratory alkalosis Administer acid to treat metabolic alkalosis

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Clinical Vignettes for the USMLE Step 1

1-34. A patient is sent to be examined by an endocrinologist after complaining of excessive thirst and increased excretion of urine. The patient is then referred to a neurologist and neuroradiologist, who detect the presence of a secondary brain lesion after viewing an MRI of the patient’s brain. Where is the most likely locus of the lesion that could account for these deficits?

a. b. c. d. e. f. g. h.

A B C D E F G H

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1-35. A 32-year-old woman presents at her physician’s office complaining of nausea and vomiting. The history reveals that her symptoms have been present for over a month and that they seem to be worse in the morning. A urine sample is taken and shows that the woman is pregnant. Physiological changes that occur during pregnancy include which of the following? a. b. c. d. e.

Decreased production of cortisol and corticosterone Increased conversion of glucose to glycogen Hypercapnia Increased hematocrit Reduced circulating gonadotropin levels

1-36. After a term uncomplicated gestation, normal delivery, and unremarkable nursery stay, a 10-day-old female is readmitted to the hospital because of poor feeding, weight loss, and rapid heart rate. Antibiotics are started as a precaution against sepsis, and initial testing indicates an unusual echocardiogram with a very short PR interval and a large heart on x-ray. Initial concern about a cardiac arrhythmia changes when a large tongue is noted, causing concern about glycogen storage disease type II (Pompe disease—232300—Table 3). Which of the following best explains why Pompe disease is more severe and lethal compared to other glycogen storage diseases? a. b. c. d. e.

The deficiency is a degradative rather than synthetic enzyme The deficiency involves a liver enzyme The deficiency involves a lysosomal enzyme The deficiency causes associated neutropenia The deficiency involves a serum enzyme

1-37. A 45-year-old woman presents with increasing fatigue, weakness, and tingling of her arms and legs. Physical examination finds numbness and loss of balance, position, and vibratory sense in both of her lower extremities. Histologic examination of a smear made from a bone marrow aspiration reveals asynchrony in red blood cell precursors between the maturation of their nuclei and their cytoplasm. Additional workup discovers achlorhydria, and a biopsy of the antrum of her stomach reveals chronic atrophic gastritis. Which of the following is the most likely diagnosis? a. b. c. d. e.

Fanconi anemia Leukoerythroblastic anemia Megaloblastic anemia Myelophthisic anemia Sideroblastic anemia

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Clinical Vignettes for the USMLE Step 1

1-38. An individual was admitted to the emergency room following loss of consciousness. After the patient regained consciousness, he was examined by a neurologist and presented with a right side hemiplegia, loss of sensation on the left side of the face, and his ability to chew. Which of the following arteries was most likely subjected to an infarct that could account for the deficits described in this individual? a. b. c. d. e.

Posterior inferior cerebellar artery Anterior inferior cerebellar artery Circumferential branches of basilar artery Paramedian branches of basilar artery Anterior spinal artery

1-39. A 34-year-old woman, who has been immobilized with a sprained ankle for the past 4 days, develops a throbbing pain that has spread to her entire left leg. History reveals that she has been taking oral contraceptives for 15 years. Compared to localized pain, such as one might experience from a needle stick, which of the following is true of ischemic pain? a. b. c. d. e.

Ischemic pain sensory fibers are classified as A delta (Ad) sensory fibers. Ischemic pain is produced by overstimulating somatic touch receptors. Ischemic pain is transmitted to the brain through the neospinothalamic tract. Ischemic pain receptors quickly adapt to a painful stimulus. Ischemic pain sensory fibers terminate within the substantia gelatinosa of the spinal cord.

1-40. A 40-year-old female reports chronic gastritis. She tests positive for H. pylori. After a course of the appropiate antibiotic theraphy her symptoms subside. Which of the following is the most effective noninvasive test for the diagnosis of Helicobacter-associated gastric ulcers? a. b. c. d. e.

Culture of stomach contents for H. pylori Detection of H. pylori antigen in stool Growth of H. pylori from a stomach biopsy Growth of H. pylori in the stool IgM antibodies to H. pylori

1-41. A 26-year-old woman has rhinorrhea, excessive lacrimation, and ocular congestion from a bout with the common cold. Diphenhydramine provides symptomatic relief. Which of the following is the most likely mechanism by which this drug gave symptom relief in the presence of this rhinovirus? a. α-Adrenergic activation (agonist) b. β-Adrenergic blockade c. Calcium channel blockade

Block 1

17

d. Histamine (H1) receptor blockade e. Muscarinic receptor blockade

1-42. A pregnant 29-year-old woman diagnosed with type I diabetes 2 decades ago, taking Humulin three times per day, is referred to the ophthalmology clinic. She is complaining of “floaters” and difficulty with night-time driving. Dilated indirect ophthalmoscopy coupled with biomicroscopy and fundus photography detect the presence of proliferative diabetic retinopathy with leaky retinal vessels indicative of increased vascular permeability, growth of new, fragile vessels on the retina and posterior surface of the vitreous and macular edema. Overexpression of fibronectin is a histological marker of diabetic microangiopathy. Which of the following is the primary function of fibronectin in the basement membrane? a. b. c. d. e.

Elasticity Cell attachment and adhesion Binding to selectins Binding to cadherins Binding to actin filaments

1-43. A 55-year-old male alcoholic presents with symptoms of liver disease and is found to have mildly elevated liver enzymes. A liver biopsy examined with a routine hematoxylin and eosin (H&E) stain reveals abnormal clear spaces in the cytoplasm of most of the hepatocytes. Which of the following materials is most likely forming these cytoplasmic spaces? a. b. c. d. e.

Calcium Cholesterol Hemosiderin Lipofuscin Triglyceride

1-44. A teenage girl is brought to the medical center complaining of fatigue that prevents participation in gym class. A consulting neurologist finds muscle weakness in the girl’s arms and legs. Laboratory testing demonstrates elevated serum triacylglycerides esterified with long-chain fatty acids and borderline low glucose. Muscle biopsy shows increased numbers of lipid vacuoles. Which of the following is the most likely diagnosis? a. b. c. d. e.

Fatty acid synthase deficiency Tay-Sachs disease Carnitine deficiency Biotin deficiency Lipoprotein lipase deficiency

18

Clinical Vignettes for the USMLE Step 1

1-45. A 2-week-old baby is hospitalized for inadequate feeding and poor growth. The parents are concerned by the child’s weak cry. An experienced grandmother accompanies them, saying she thought the cry sounded like a cat’s meow. The grandmother also states that the baby doesn’t look much like either parent. The physician orders a karyotype after noting a small head size (microcephaly) and subtle abnormalities of the face. Which of the results pictured below is most likely?

a. b. c. d. e.

Result A Result B Result C Result D Result E

Block 1

19

1-46. A woman has severe irritable bowel syndrome characterized by frequent, profuse, and symptomatic diarrhea. She has not responded to firstline therapies and is started on alosetron. Which of the following is the most worrisome adverse effect associated with this drug? a. b. c. d. e.

Cardiac arrhythmias (serious, e.g., ventricular fibrillation) Constipation, bowel impaction, ischemic colitis Parkinsonian extrapyramidal reactions Pulmonary fibrosis Renal failure

1-47. A patient with renal failure is undergoing periodic hemodialysis while awaiting a transplant. Between dialysis sessions we want to reduce the body’s phosphate load by reducing dietary phosphate absorption and removing some phosphate already in the blood. Which of the following drugs would be most suitable for this purpose? a. b. c. d. e.

Aluminum hydroxide Bismuth subsalicylate Magnesium hydroxide/oxide Sodium bicarbonate Sucralfate

1-48. Histologic sections from a 3-cm mass found in the mandible of a 55year-old woman reveal a tumor consisting of nests of tumor cells that appear dark and crowded at the periphery of the nests and loose in the center (similar to the stellate reticulum of a developing tooth). Grossly, the lesions consist of multiple cysts filled with a thick, “motor oil”–like fluid. Which of the following is the most likely diagnosis? a. b. c. d. e.

Pleomorphic adenoma Ameloblastoma Mucoepidermoid carcinoma Adenoid cystic carcinoma Acinic cell carcinoma

20

Clinical Vignettes for the USMLE Step 1

1-49. A 24-year-old woman presents after having several “attacks” that last for about 24 h. She states that during these attacks she develops nausea, vomiting, vertigo, and ringing in her ears. Physical examination reveals a sensorineural hearing loss. Which of the following is the most likely cause of this woman’s signs and symptoms? a. b. c. d. e.

Acute suppurative inflammation of the middle ear Dilation of the cochlear duct and saccule Obstruction of the middle ear by a cyst filled with keratin Destruction of the tympanic membrane by a benign neoplasm New bone formation around the stapes and the oval window

1-50. A 2-month-old male infant, who was born at term without any prenatal abnormalities, is being evaluated for possible visual problems. He is noted to have an abnormal white light reflex involving his right eye, and examination finds a large mass that has almost completely filled the posterior chamber of this eye. Which of the following cells are most likely to be seen proliferating in histologic sections from this mass? a. b. c. d. e.

Benign fibroblasts and endothelial cells Foamy macrophages with cytoplasmic clear vacuoles Plasmacytoid cells within a dense Congo red–positive stroma Small cells forming occasional rosette structures Spindle-shaped cells with cytoplasmic melanin

Block 2 Questions 2-1. Parents bring in their 2-week-old child fearful that he has ingested a poison. They had delayed disposing one of the child’s diapers, and noted a black discoloration where the urine had collected. Later, they realized that all of the child’s diapers would turn black if stored as waste for a day or so. Knowing that phenol groups can complex to form colors, which of the following amino acid pathways are implicated in this phenomenon? a. b. c. d. e.

The phenylalanine, tyrosine, and homogentisate pathway The histidine pathway The leucine, isoleucine, and valine pathway The methionine and homocystine pathway The arginine and citrulline pathway (urea cycle)

2-2. A 6-month-old boy is being evaluated for a lesion on his chin. Physical examination finds a raised, nontender, bright red strawberry-colored vascular lesion measuring approximately 4 mm in greatest dimension. At this time, which of the following is the best therapy for this infant? a. b. c. d. e.

Leave alone and follow up on a routine basis Photocoagulation with yellow-green laser light Repeated injections with steroids Shave biopsy with frozen section diagnosis Wide local excision with sentinel node sampling

21

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22

Clinical Vignettes for the USMLE Step 1

2-3. A 52-year-old male develops an abscess following surgery to repair an abdominal gunshot wound. Gram stain of the exudates from his foulsmelling abscess reveals numerous polymorphonuclear neutrophils (PMNs) and several gram-negative rods that did not grow on blood plates in the presence of O2. Metabolism of O2 results in toxic reactive oxygen species. Which of the following enzymes is most likely involved in the following reaction? 2O2− + 2H+ → H2O2 + O2 a. b. c. d. e.

ATPase Catalase Oxygen permease Peroxidase Superoxide dismutase

2-4. A 49-year-old male in end-stage renal failure is able to perform peritoneal dialysis at home. The osmolality of the solution chosen for peritoneal dialysis will determine the rate of ultrafiltration. Which of the following statements best characterizes a molecule whose osmolality is zero? a. b. c. d. e.

It will not permeate the membrane It can only cross the membrane through the lipid bilayer It causes water to flow across the membrane It is as diffusible through the membrane as water It is transported across the membrane by a carrier

2-5. A 26-year-old African American woman presents with nonspecific symptoms including fever, malaise, and increasing respiratory problems. A chest x-ray reveals enlarged hilar lymph nodes, while laboratory tests find her serum calcium level to be elevated. A transbronchial biopsy reveals scattered chronic inflammatory cells, reactive epithelial changes, and several noncaseating granulomas. The pathomechanism involved in the formation of these noncaseating granulomas involves the activation of macrophages to form epithelial cells by the action of which substance? a. b. c. d. e.

Gamma-interferon Leukotriene C4 Interleukin-2 Interleukin-5 Interleukin-12

Block 2

23

2-6. A nurse develops clinical symptoms consistent with hepatitis. She recalls sticking herself with a needle approximately 4 months before, after drawing blood from a patient. Serologic tests for HBsAg, antibodies to HBsAg, and hepatitis A virus (HAV) are all negative; however, she is positive for IgM core antibody. Which of the following characterizes the current health state of the nurse? a. b. c. d. e.

Does not have hepatitis B Has hepatitis A Has hepatitis C Is in the late stages of hepatitis B infection Is in the “window” (after the disappearance of HBsAg and before the appearance of anti–HBsAg)

2-7. A 10-year-old boy is brought into your office by his mother. The boy is supporting his left arm at the elbow by using his right hand because he thinks he has “broken his arm.” The 10-year-old had been playing tag and tripped over the curb and landed on the grass, catching himself with his hands. Upon physical examination you note a slight drooping of the left shoulder when unsupported, and tenderness over the midclavicular region but no palpable fracture or displacement. The jugular notch appears symmetrical. The shoulder has normal movement, but the boy is unwilling to lift his hand above his head because it hurts. Otherwise, hand and arm movements are relatively normal with normal sensation. You order an AP and lateral x-rays of the thorax and upper arm because you suspect which of the following? a. b. c. d. e.

Colles’ fracture Scaphoid fracture Fracture of the surgical head of the humerus Dislocated sternoclavicular joint Greenstick fracture of the clavicle

24

Clinical Vignettes for the USMLE Step 1

2-8. A 65-year-old obese male presents with pain radiating down the left arm and shortness of breath. A serum lactate dehydrogenase (LDH) level is obtained to evaluate possible myocardial infarction, and its activity is only slightly elevated. Shortly thereafter the laboratory calls, saying that a more detailed analysis of LDH does suggest myocardial damage. The managing physician knows that lactate dehydrogenase is composed of two different polypeptide chains arranged in the form of a tetramer. Which of the following is the likely correlation between LDH measures and the likelihood of myocardial infarction? a. LDH is an enzyme specific to the endocardium b. LDH is mainly localized in liver, and its elevation in cardiac disease occurs because of heart failure c. LDH isozymes are composed of different subunit combinations, some released during inflammation following heart attacks d. LDH isozymes are composed of different subunit combinations, some specific for heart and released with myocardial damage e. LDH isozymes are composed of different subunit combinations, some specific for vascular endothelium and released with infarction

2-9. A patient with a family history of peripheral neuropathy is found to have a decrease in nerve conduction velocity and an X-linked mutation of connexin 32, consistent with Charcot-Marie-Tooth Disease. Connexin is an important component of which of the following? a. b. c. d. e.

Gap junction Sarcoplasmic reticulum Microtubule Synaptic vesicle Sodium channel

2-10. A 67-year-old female was admitted to a hospital after she reported to her primary care physician that she had been having very painful headaches. Further examination revealed the presence of significant increases in intracranial pressure. After viewing a magnetic resonance imaging (MRI), the neurologist concluded that the woman’s condition was due to the presence of a developing tumor along the rostral aspect of the medial wall of the lateral ventricle. Which of the structures in the illustration would be most likely to contain this tumor?

Block 2

a. b. c. d. e.

A B C D E

f. g. h. i.

25

F G H I

2-11. Your patient has bipolar illness, hypercholesterolemia, chronic-stable angina, and Stage I essential hypertension. He has been taking lithium and an SSRI for the bipolar illness. Cardiovascular drugs include atorvastatin, diltiazem, sublingual nitroglycerin, captopril, and hydrochlorothiazide. Which of the following outcomes, due to interactions involving these drugs, would you most likely expect? a. Development of acute psychosis from an ACE inhibitor-antipsychotic interaction b. Development of a hypomanic state from antagonism of lithium’s action by the nitroglycerin c. Lithium toxicity because of hyponatremia caused by the hydrochlorothiazide d. Loss of cholesterol control from antagonism of the HMG CoA reductase inhibitor by the antipsychotic e. Worsening of angina because the antipsychotic counteracts the effects of the calcium channel blocker f. Worsening of angina because the lithium antagonizes the effects of the nitroglycerin

26

Clinical Vignettes for the USMLE Step 1

2-12. A hospital worker is found to have hepatitis B surface antigen. Subsequent tests reveal the presence of e antigen as well. Which of the following best describes the worker? a. b. c. d. e.

Is infective and has active hepatitis Is infective but does not have active hepatitis Is not infective Is evincing a biologic false-positive test for hepatitis Has both hepatitis B and hepatitis C

2-13. A 59-year-old woman presents with headaches and decreasing vision over the past several months. Her children state that she has been bumping into things recently and does not seem to see them when they are not directly in front of her. Physical examination is unremarkable except for the visual field abnormality illustrated in the picture. Her visual problems are most likely to be caused by a tumor originating in which one of the following anatomic areas? Left

a. b. c. d. e.

Right

Parietal lobe Pineal gland Pituitary gland Posterior orbit Temporal lobe

2-14. A 23-year-old female presents with fatigue and is found to have a systolic murmur and higher than normal cardiac output. The differential diagnosis based on these findings includes which of the following? a. b. c. d. e.

Hypertension Mitral valve prolapse Anemia Aortic regurgitation Cardiac tamponade

Block 2

27

2-15. On November 6, a patient had the onset of an illness characterized by fever, chills, headache, cough, and chest pain. The illness lasted 1 week. On December 5, she had another illness very similar to the first, which lasted 6 days. She had no flu immunization during this period. Her hemagglutination inhibition (HI) antibody titer to swine flu virus was as follows: November 6 10 November 30 10 December 20 160 (There was no laboratory error) Which of the following is the best conclusion from these data? a. The patient was ill with swine flu on November 6 b. The patient was ill with swine flu later, and the November 6 illness was due to another pathogen c. The patient was ill with swine flu on December 20 d. It is impossible to relate either illness with the specific virus

2-16. A 6-month-old male becomes ill after fruits and vegetables are added to his diet of breast milk. Mother feels that he used to become colicky when she ate fruit, although her pediatrician did not think this was significant. After 1 month of these new foods, the child has stopped gaining weight and the pediatrician feels an enlarged liver. Initial blood tests show a mild acidosis (pH 7.2) with increased lactic acid and low blood glucose. The Clinitest reaction is positive for reducing substances in the urine, but the glucose oxidase test is negative for glucosuria. A glycogen storage disease is suspected, and a liver biopsy dose shows mildly increased glycogen with marked cellular damage suggestive of early cirrhosis. Assays for type IV glycogen storage disease are negative (Table 3), and the initial frozen urine sample is reanalyzed and found to contain fructose. The most likely diagnosis and the reasons for hypoglycemia and glycogen accumulation is which of the following? a. b. c. d. e.

Hereditary fructose intolerance with inhibition of liver phosphorylase Hereditary fructose intolerance with inhibition of glycogen synthase Essential fructosuria with inhibition of glycogen synthase Essential pentosuria with inhibition of liver phosphorylase Essential fructosuria with allosteric stimulation of glycogen synthase

28

Clinical Vignettes for the USMLE Step 1

2-17. A pregnant woman is found to have elevated blood pressure on her check-up at 8 months gestation, and testing by her obstetrician demonstrates anemia with Hemolysis, Elevated Liver enzymes, and Low Platelets that are characteristic of disease represented by the acronym HELLP syndrome. The woman is hospitalized and fetal maturity tests are performed that allow elective premature delivery. The woman quickly recovers but the premature newborn has a dilated heart and elevated liver enzymes that are characteristic of a defect in long chain fatty acid oxidation. The potential enzyme deficiencies are those responsible for sequential oxidation of fatty acids, which include which of the following? a. b. c. d. e.

Dehydrogenase, hydratase, dehydrogenase, thiolase Transacylase, synthase, reductase Hydratase, reductase, thioesterase Thioesterase, dehydrogenase, thiolase Dehydrogenase, thiolase, thioesterase

2-18. A patient with elevated heart rate and blood pressure is examined by a battery of physicians and they conclude that his condition is due to a deficiency or loss of the carotid sinus reflex. Which of the following is a component of this reflex? a. b. c. d. e.

Baroreceptor afferent fibers from cranial nerve XI Glossopharyngeal efferent fibers Interneurons within the nucleus ambiguus of the medulla Efferent fibers contained in the intermediate component of the facial nerve Vagal efferent fibers

2-19. A young couple comes to your urology office because of inability to conceive a wanted child after 1 year of unprotected sex. The wife had already undergone a gynecological workup, including testing for 3 months showing a normal ovulation profile as confirmed by an ovulatory kit. The primary care physician describes the husband’s physical exam as normal and had already ordered a semen analysis and had forwarded the results to you. The semen volume was 0.5 mL, pH 6.8, and azospermic without any fructose. The husband has a brother, who has two children, one of whom has confirmed cystic fibrosis. You order a pelvic MRI of the husband to determine whether which of the following exist(s)? a. b. c. d. e.

Bilateral abdominal testicles Hypospadias Congenital absence of ejaculatory ducts and vas deferens Congenital hydrocele Congenital absence of the prostate gland

Block 2

29

2-20. A 37-year-old obese man presents with signs and symptoms of hyperglycemia. After appropriate workup, he is diagnosed as having type II diabetes mellitus, which is due in part to insulin resistance. Laboratory evaluation of his serum also finds hypertriglyceridemia, which is due to his diabetes. The most common type of secondary hyperlipidemia associated with diabetes mellitus is characterized by elevated serum levels of which one of the following substances? a. b. c. d. e.

Chylomicrons High-density lipoproteins Intermediate-density lipoproteins Low-density lipoproteins Very-low-density lipoproteins

2-21. A newborn girl is born with a small mouth, rather widely spaced eyes and low-set ears. Genetic analysis shows a microdeletion on chromosome 22q11.2 leading to a diagnosis of an anomaly which results from failure of the normal development of the third and fourth branchial pouches during embryonic development. Which of the following would be expected to occur in a child with this anomaly? a. b. c. d. e.

Absence of the parafollicular cells Increased numbers of cells in the deep cortex of the lymph nodes Tetany Excess activity of osteoclasts Increased Ca2+ levels in the blood

2-22. A 64-year-old male was admitted to the hospital with edema and congestive heart failure. He was found to have diastolic dysfunction characterized by inadequate filling of the heart during diastole. The decrease in ventricular filling is due to a decrease in ventricular muscle compliance. Which of the following proteins determines the normal stiffness of ventricular muscle? a. b. c. d. e.

Calmodulin Troponin Tropomyosin Titin Myosin light chain kinase

30

Clinical Vignettes for the USMLE Step 1

2-23. A family routinely consumed unpasteurized milk, claiming “better taste.” Several members experienced a sudden onset of crampy abdominal pain, fever, and bloody, profuse diarrhea. C. jejuni was isolated and identified from all patients. Which of the following is the treatment of choice for this type of enterocolitis? a. b. c. d. e.

Ampicillin Campylobacter antitoxin Ciprofloxacin Erythromycin Pepto-Bismol

2-24. A family is seen for routine prenatal counseling because the mother of two normal children is age 35, the arbitrary “advanced maternal age” when the approximate 1 in 100 risk for fetal chromosome disorders is deemed significant. Family history reveals that the mother’s parents and her husband all have had onset of high blood pressure (hypertension) at early ages, and two of mother’s grandparents died of strokes that may be hypertension-related. The mother also had some hypertension in the third trimester of her last pregnancy. Recognizing that hypertension is a multifactorial trait, which of the following is the most appropriate explanation and counseling for the couple? a. Multifactorial determination indicates an interaction between the environment and a single gene, implying a 50% risk for eventual hypertension in mother and offspring b. Multifactorial determination indicates an interaction between the environment and multiple genes, implying a 5–10% risk for eventual hypertension in mother and offspring c. Multifactorial determination results from multiple postnatal environmental factors, implying a 75–100% risk for eventual hypertension in mother and a 5–10% risk to offspring d. Multifactorial determination results from multiple pre- and postnatal environmental factors, implying a 75–100% risk for eventual hypertension in mother and a 5–10% risk to offspring e. Multifactorial determination implies action of multiple genes independent of environmental factors, implying low risks for hypertension in mother’s next pregnancy but a 5–10% risk for eventual hypertension in offspring

2-25. A 23-year-old woman develops the sudden onset of congestive heart failure. Her condition rapidly deteriorates and she dies in heart failure. At autopsy, patchy interstitial infiltrates composed mainly of lymphocytes are found, some of which surround individual myocytes. Which of the following is the most likely cause of this patient’s heart failure?

Block 2

a. b. c. d. e.

31

Autoimmune reaction (to group A β-hemolytic streptococci) Bacterial myocarditis (due to S. aureus infection) Hypersensitivity myocarditis (due to an allergic reaction) Nutritional deficiency (due to thiamine deficiency) Viral myocarditis (due to coxsackievirus infection)

2-26. An apathetic male infant in an underdeveloped country is found to have peripheral edema, a “moon” face, and an enlarged, fatty liver. Which of the following is the basic defect causing this change in the liver? a. b. c. d. e.

Decreased protein intake leads to decreased lipoproteins Decreased caloric intake leads to hypoalbuminemia Decreased carbohydrate intake leads to hypoglycemia Decreased fluid intake leads to hypernatremia Decreased fat absorption leads to hypovitaminosis

2-27. An 18-year-old girl with a 9-year history of wheezing on exertion is referred for pulmonary function tests. The diagram below represents the spirometry tracing of a forced vital capacity. Her total lung capacity was 110% of predicted. Which of the following values will most likely be above normal?

a. b. c. d. e.

Vital capacity Residual volume Expiratory reserve volume FEV1.0 /FVC Maximum voluntary ventilation

32

Clinical Vignettes for the USMLE Step 1

2-28. A 5-year-old boy sustains a tear in his gastrocnemius muscle when he is involved in a bicycle accident. Regeneration of the muscle will occur through which of the following? a. b. c. d. e.

Differentiation of satellite cells Dedifferentiation of myocytes into myoblasts Fusion of damaged myofibers to form new myotubes Hyperplasia of existing myofibers Differentiation of fibroblasts to form myocytes

2-29. A 45-year-old male is hospitalized for treatment of myocardial infarction. His father and a paternal uncle also had heart attacks at an early age. His cholesterol is elevated, and lipoprotein electrophoresis demonstrates an abnormally high ratio of low- to high-density lipoproteins (LDL to HDL). Which of the following is the most likely explanation for this problem? a. b. c. d. e.

Mutant HDL is not responding to high cholesterol levels Mutant LDL is not responding to high cholesterol levels Mutant caveolae proteins are not responding to high cholesterol levels Mutant LDL receptors are deficient in cholesterol uptake Intracellular cholesterol is increasing the number of LDL receptors

2-30. A 48-year-old man who has a long history of excessive drinking presents with signs of alcoholic hepatitis. Microscopic examination of a biopsy of this patient’s liver reveals irregular eosinophilic hyaline inclusions within the cytoplasm of the hepatocytes. These eosinophilic inclusions are composed of which one of the following substances? a. b. c. d. e.

Immunoglobulin Excess plasma proteins Prekeratin intermediate filaments Basement membrane material Lipofuscin

2-31. A febrile 52-year-old male patient receiving glucocorticoid treatment presents with vesicular lesions with intense itching, burning, and sharp pain along the back in a specific dermatomal pattern covering his nipple and extending onto the right side of his back. The vesicular lesions do not cross the midline. A Tzanck test is positive. The cause of this illness is the movement of virus from the structures shown in the photomicrograph toward the surface of the skin. This movement occurs in which direction and by which molecular motor?

Block 2

a. b. c. d. e.

33

Minus end to plus end, dynein Minus end to plus end, kinesin Plus end to minus end, dynein Plus end to minus end, kinesin Minus end to plus end, myosin II

2-32. A 59-year-old male with an ejection fraction of 15%, who is being treated with medications for his heart failure, is asked whether he would like to participate in a trial for an experimental drug. The drug being tested is designed to decrease the expression of phospholamban on ventricular muscle cells. Which of the following would be increased by decreasing phospholamban? a. b. c. d. e.

The activity of the sodium-potassium pump The diastolic stiffness of the ventricular muscle cells The activity of the L-type calcium channels The duration of the ventricular muscle action potential The concentration of calcium within the SR

2-33. Several employees in a veterinary facility experienced a mild influenza-like infection after working on six sheep with an undiagnosed illness. The etiologic agent causing the human disease is most often transmitted to humans by which of the following methods? a. b. c. d. e.

Fecal contamination from flea deposits on the skin Inhalation of infected aerosols from animal urine and feces Lice feces scratched into the broken skin during the louse’s blood feeding Tick saliva during feeding on human blood Urethral discharge from infected humans

34

Clinical Vignettes for the USMLE Step 1

2-34. A 65-year-old man who just retired after having worked for many years as a shipyard worker presents with increasing shortness of breath. Pertinent medical history is that he has been a long time smoker. A CT scan of his chest reveals thick, pleural plaques on the surface of his lungs. The associated picture is from a bronchial washing specimen from this patient. The dumbbellshaped structures in this picture were found to stain blue with a Prussian blue stain. What are these structures?

a. b. c. d. e.

Candida species Cholesterol crystals Ferruginous bodies Schaumann bodies Silica particles

2-35. Emma is a 64-year-old woman who has had heart disease for many years. While carrying chemicals down the stairs of the dry-cleaning shop where she works, she suddenly lost control of her right leg and arm. She fell down the stairs and was able to stand up with some assistance from a coworker. When attempting to walk on her own, she had a very unsteady gait, with a tendency to fall to the right side. Her supervisor asked her if she was all right, and noticed that her speech was very slurred when she tried to answer. He called an ambulance to take her to the nearest hospital. Upon admission, her face appears symmetric, but when asked to protrude her tongue, it deviates toward the left. She is unable to tell if her right toe is moved up or down by the physician when she closes her eyes, and she can’t feel the buzz of a tuning fork on her right arm and leg. In addition, her right arm and leg are markedly weak. The physician can find no other abnormalities in the remainder of Emma’s general medical examination.

Block 2

35

Where in the nervous system could a lesion occur that would cause arm and leg weakness but spare the face? a. b. c. d. e.

Right corticospinal tract in the cervical spinal cord Left inferior frontal lobe Right medullary pyramids Occipital lobe Right side of basilar pons

2-36. A 43-year-old anatomy professor is working in her garden, pruning rose bushes without gloves. She has a thorn enter the skin of her forefinger. The area later becomes infected and she removes the thorn, but there is still pus remaining at the wound site. Which of the following cells functions in the formation of pus?

a. b. c. d. e. f.

A B C D E F

36

Clinical Vignettes for the USMLE Step 1

2-37. Valley fever or desert rheumatism is asymptomatic in 60% of individuals, while 40% present with a self limited influenza-like illness with fever, malaise, cough, arthralgia, and headache. Less than 1% develop lifethreatening CNS complications. The highly infectious asexual conidia of the etiologic agent are called which of the following? a. b. c. d.

Arthroconidia Blastoconidia Chlamydospores Sporangiospores

2-38. A morbidly obese person visits the local bariatric (weight loss) clinic seeking a pill that will help shed weight. The physician prescribes dextroamphetamine. In addition to causing its expected centrally mediated anorexigenic (appetite-suppressant) effects it causes a host of peripheral adrenergic effects that, for some patients, can prove fatal. Which of the following best summarizes the main mechanism by which dextroamphetamine, or amphetamines in general, cause their peripheral autonomic effects? a. b. c. d. e.

Activates MAO Blocks NE reuptake via the amine pump/transporter Displaces, releases, intraneuronal NE Enhances NE synthesis, leading to massive neurotransmitter overproduction Stabilizes the adrenergic nerve ending by directly activating α2 receptors

2-39. A 1-year-old child recently emigrated from Africa exhibits intermittent diarrhea, pallor (pale skin), extreme tenderness of the bones, “rosary” of lumps along the ribs, nose bleeds, bruising over the eyelids, and blood in the urine. Which of the following is the most likely cause? a. b. c. d.

Deficiency of vitamin C due to a citrus-poor diet during pregnancy Hypervitaminosis A due to ingestion of beef liver during pregnancy Deficiency of vitamin C because of reliance on a milk only diet Deficiency of vitamin K because of neonatal deficiency and continued poor nutrition e. Deficiency of vitamin D due to darker skin pigmentation and poor sun exposure

2-40. An experiment was performed by a physiologist who was interested in identifying a specific kind of neuron within the visual cortex. The type of neuron sought by the investigator was one that responds to an image in a specific position, has discrete excitatory and inhibitory zones, and is associated with a specific axis of orientation. Which of the following cells would respond to such an image?

Block 2

a. b. c. d. e.

37

M cells of the lateral geniculate nucleus P cells of the lateral geniculate nucleus Simple cells of the visual cortex Complex cells of the visual cortex Hypercomplex cells of the visual cortex

2-41. A patient stung by a bee is rushed into the emergency room with a variety of symptoms including increasing difficulty in breathing due to nasal and bronchial constriction. Although your subsequent treatment is to block the effects of histamine and other acute-phase reactants released by most cells, you must also block the slow-reacting substance of anaphylaxis (SRS-A), which is the most potent constrictor of the muscles enveloping the bronchial passages. An SRS-A is composed of which of the following? a. b. c. d. e.

Thromboxanes Interleukins Complement Leukotrienes Prostaglandins

2-42. A 56-year-old man presents to his family medicine physician. He is a 41 year pack/day smoker. He reports that he has had a “typical smoker’s cough” for years; however, the morning cough has turned into a chronic productive cough with hemoptysis. He has dyspnea, chest pain, cachexia, increasing dysphonia. He has been treated for 4 respiratory infections in the past 18 months. Examination of the sputum reveals the presence of malignant cells confirmed by fine needle aspiration. Imaging reveals a tumor that is 3 cm in greatest dimension, surrounded by lung parenchyma. Bronchoscopic evaluation reveals a cavitary lesion of a proximal bronchus. Surgical resection is completed and the pathologist classifies the tumor as a T1, N2, MO nonsmall cell lung cancer (NSCLC), specifically a squamous cell carcinoma. Tumor vascularity assessed by bronchial arteriography (BAG) and immunocytochemistry indicates a highly vascular tumor with many microvessels. Vascularity of the tumor is inhibited by upregulation of which of the following? a. b. c. d. e.

Vascular endothelial growth factor (VEGF) Platelet-derived growth factor (PDGF) Extracellular matrix synthesis Endostatin Periendothelial cell recruitment and proliferation

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Clinical Vignettes for the USMLE Step 1

2-43. A couple has three girls, the last of whom is affected with cystic fibrosis. The first-born daughter marries her first cousin—that is, the son of her mother’s sister—and they have a son with cystic fibrosis. The father has a female cousin with cystic fibrosis on his mother’s side. Which of the following pedigrees represents this family history?

a. b. c. d. e. f. g. h.

Diagram A Diagram B Diagram C Diagram D Diagram E Diagram F Diagram G Diagram H

Block 2

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2-44. A 65-year-old man with uncontrolled Type II diabetes and sustained hyperglycemia (serum glucose = 550 mg/dL) and polyuria (5 L/day) is evaluated in the hospital’s clinical laboratory because his urine glucose concentration (