Clinical Vignettes for the USMLE Step 1 PreTestTM Self-Assessment and Review Fourth Edition pot

Which ofthe following is the most likely diagnosis?... Which meningi-of the following is the most likely cause meningi-of the disease?. Which of the following body results would be most

Clinical Vignettes for the

USMLE Step 1

PreTestTM

Self-Assessment and Review

Medicine is an ever-changing science As new research and clinical experience broaden our knowledge, changes in treatment and drug therapy are required The authors and the publisher of this work have checked with sources believed to be reliable in their efforts to provide information that is complete and generally in accord with the standards accepted at the time of publication However, in view of the possibility of human error or changes in medical sciences, neither the authors nor the publisher nor any other party who has been involved in the preparation or publication of this work warrants that the information contained herein is in every respect accurate or complete, and they disclaim all responsibility for any errors or omissions or for the results obtained from use of the information contained in this work Readers are encouraged to confirm the information contained herein with other sources For example and in particular, readers are advised to check the product information sheet included in the package of each drug they plan to administer

to be certain that the i nformation contained in this work is accurate and that changes have not been made in the recommended dose or in the contraindications for administration This recommendation is of particular importance in connection with new or infrequently used drugs.

Clinical Vignettes for the

of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher

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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

v

The current format of the United States Medical Licensing ExaminationStep 1 (USMLE Step 1) exam emphasizes clinical vignettes—in single-best-answer multiple-choice format—as the only test question The examina-tion 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 coveringthe core basic sciences and was assembled based on the published contentoutline 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 allcore basic science areas Answers are in the second half of the book Eachanswer is accompanied by a concise but comprehensive explanation and isreferenced 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-HillNovember 2007

vii

Copyright © 2008 by The McGraw-Hill Companies, Inc Click here for terms of use

Block 1

Questions

of recent-onset ventricular ectopy, second degree AV nodal block, matopsia, and other extracardiac signs and symptoms of digoxin intoxica-tion His family doctor, who has been treating him for a host of commonmedical problems over the last 30 years, had prescribed furosemide anddigoxin for this gentleman’s heart failure Blood tests show that serum digoxinlevels are well within a normal range We believe the problems are diuretic-induced Which of the following does the diuretic most likely do to accountfor the digoxin toxicity?

chro-a Caused hypercalcemia

b Caused hypokalemia

c Caused hyponatremia

d Displaced digoxin from tissue binding sites

e Inhibited digoxin’s metabolic elimination

weakness in his arms and legs A battery of tests are administered to thepatient, including those involving nerve conduction The nerve conductiontest reveals a reduction in the compound motor action potential relating tomuscles of the hand However, the amplitude of this potential improvessignificantly following exercise involving the relevant muscles Which ofthe following is the most likely diagnosis?

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 nancy was complicated by preeclampsia, but fetal monitoring and ultrasoundwere normal throughout gestation The predominant structures shown in theaccompanying photomicrograph of the placenta are derived from which of thefollowing?

preg-a A combination of fetal and maternal tissues

b Endometrial glands

c Endometrial stroma

d Fetal tissues

e Maternal blood vessels

brought to the Emergency Department after her husband discovered herunresponsive and barely breathing when he stopped at home from workduring his lunch hour A bottle of Vicodin was found next to the bathroomsink Which of the following arterial blood gases are most consistent withher clinical presentation?

a pH = 7.27; Pa CO 2 = 60 mmHg, [HCO 3 ] = 26 mEq/L, Anion Gap = 12 mEq/L

b pH = 7.02; Pa CO = 60 mmHg, [HCO ] = 15 mEq/L, Anion Gap = 12 mEq/L

c pH = 7.10; Pa CO2= 20 mmHg, [HCO 3 ] = 6 mEq/L, Anion Gap = 30 mEq/L

d pH = 7.51; Pa CO 2 = 49 mmHg, [HCO 3 ] = 38 mEq/L, Anion Gap = 14 mEq/L

e pH = 7.40; Pa CO2= 20 mmHg, [HCO 3 ] = 10 mEq/L, Anion Gap = 26 mEq/L

1-5. A 6-month old infant is admitted to the hospital with acute tis The Gram stain reveals gram-positive, short rods, and the mother indi-cates that the child has received “all” of the meningitis vaccinations Which

meningi-of the following is the most likely cause meningi-of the disease?

clini-cal diagnosis of Toxoplasma encephalitis is made, and Toxoplasma cysts are

observed in a brain section (see figure below) Which of the following body results would be most likely in this patient?

anti-a IgM nonreactive, IgG nonreactive

b IgM nonreactive, IgG reactive (low titer)

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

d IgM reactive (high titer), IgG reactive (high titer)

e IgM reactive (high titer), IgG nonreactive

1-7. A 14-month-old boy presents with a fever of 102°F The child has alongstanding history of recurrent lower respiratory tract infections includ-ing bronchitis and pneumonia Chronic diarrhea is a longstanding prob-lem His mother reports that she had numerous upper respiratoryinfections 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 25mg/dL (normal = 40–60 mg/dL) There are numerous neutrophils andother white cells in the stool sample and the stool is cultured for specificbacteria IgA coats pathogens facilitating repulsion of the negative charge

on the cell membrane That negative charge on the cell membrane is marily caused by which of the following?

pri-a Free saccharide groups

b Glycoprotein

c Cholesterol

d Peripheral membrane protein

e Integrins

leg cramps He is not currently taking any medications Physical tion finds a thin adult man with mild hypertension Laboratory examina-tion reveals slightly increased sodium, decreased serum potassium level,and decreased hydrogen ion concentration Serum glucose levels are withinnormal limits A CT scan reveals a large tumor involving the cortex of hisleft adrenal gland Which of the following combinations of serum labora-tory findings is most likely to be present in this individual?

examina-a Decreased aldosterone with increased renin

b Decreased cortisol with decreased ACTH

c Increased aldosterone with decreased renin

d Increased cortisol with increased ACTH

e Increased deoxycorticosterone with increased cortisol

1-9. Following hemisection of the spinal cord at the level of approximatelyT3, a patient experiences loss of pain and temperature on the left side of theleg Which of the following tracts was affected by the hemisection of thecord that could account for this deficit?

a Right fasciculus cuneatus

b Right fasciculus gracilis

c Right spinothalamic tract

d Left spinothalamic tract

e Left corticospinal tract

1-10. A 27-year-old patient with insulin-dependent diabetes mellitus told hisroommate 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 aweekend trip on Sunday evening, he found the man unresponsive on thecouch, and called 9-1-1 Which of the following arterial blood gases taken inthe Emergency Department would be expected in diabetic coma?

a pH = 7.22; Pa CO 2 = 60 mmHg, [HCO 3 ] = 26 mEq/L, Anion Gap = 12 mEq/L

b pH = 7.02; Pa CO2= 60 mmHg, [HCO 3 ] = 15 mEq/L, Anion Gap = 12 mEq/L

c pH = 7.10; Pa CO 2 = 20 mmHg, [HCO 3 ] = 6 mEq/L, Anion Gap = 30 mEq/L

d pH = 7.51; Pa CO2= 49 mmHg, [HCO 3 ] = 38 mEq/L, Anion Gap = 14 mEq/L

e pH = 7.40; Pa CO 2 = 20 mmHg, [HCO 3 ] = 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 ofthe cardiac valvular abnormality present in this individual?

a Dorsal motor nucleus of the vagus

b Nucleus ambiguus

c Inferior salivatory nucleus

d Superior salivatory nucleus

e Edinger-Westphal nucleus of cranial nerve III

1-13. An immunocompromised person with a history of seizures has anMRI that reveals a temporal lobe lesion Brain biopsy results show multin-ucleated giant cells with intranuclear inclusions Which of the following isthe most probable cause of the lesion?

of her peripheral blood reveals red granules (Schüffner’s dots) in enlarged,

young erythrocytes Which of the following organisms is most likely tohave produced her signs and symptoms?

An electroretinogram (ERG) is reduced in amplitude The cause may berelated to a failure of opsin and other protein vesicle transport This transportwould occur along which of the following?

a Microfilaments (thin filaments)

the local concentration of which of the following agents will cause systemicvasoconstriction?

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, dominant- acting 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.

1-19. A 48-year-old woman presents with a 1.5-cm firm mass in the upperouter quadrant of her left breast A biopsy from this mass reveals many ofthe ducts to be filled with atypical cells In the center of these ducts there

is extensive necrosis No invasion into the surrounding fibrous tissue isseen Which of the following is the most likely diagnosis?

a Colloid carcinoma

b Comedocarcinoma

c Infiltrating ductal carcinoma

d Infiltrating lobular carcinoma

e 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?

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

as uncharacteristically slow to learn and react and shying away from thing new, preferring the familiar, confused, getting lost easily, and exercis-ing poor judgment He scores poorly on the mini-mental status examination(MMSE) This disease is believed to be caused by protein misfolding Chap-eronins regulate protein folding in which of the following ways?

any-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

1-24. A 17-year-old boy is admitted to the hospital with a traumatic braininjury, 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 mostlikely due to a lesion of which of the following?

a The lateral hypothalamus

b The arcuate nucleus

c The posterior nucleus

d The paraventricular nucleus

e The anterior hypothalamus

1-25. A 3-year-old girl, with no history of vaccination, is brought to the pital with a sore throat, fever, malaise, and difficulty breathing Physicalexamination reveals a gray membrane covering the pharynx Growth of theetiologic agent on cysteine-tellurite agar forms gray to black colonies with abrown halo The major virulence factor of this organism is only produced bythose strains that will most likely have which of the following characteristics?

hos-a Encapsulated

b Glucose fermenters

c Lysogenic for β-prophage

d Of the mitis strain

e Sucrose fermenters

1-26. A patient with epilepsy is started on oral therapy with an appropriateanticonvulsant Not long after treatment starts he manifests psychotic behav-iors that were not present before antiepileptic drug therapy started Of thefollowing antiepileptic agents, which is associated with the highest risk ofcausing psychosis?

a Assembly of ribosomal subunits into mature ribosomes

b Translation of cytosolic proteins

c Transcription of nuclear proteins

d Transcription of ribosomal proteins

e Organelle degradation

1-28. A 34-year-old man with mild anxiety and depression symptoms hasheard about buspirone on television and asks whether it might be suitable forhim According to the latest diagnostic criteria, the drug would be appropri-ate, particularly for short-term symptom control Which of the following bestdescribes 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

1-29. A 47-year-old female is brought to the Emergency Departmentbecause she fainted at the gym during her daily aerobic workout A promi-nent systolic murmur is heard and a presumptive diagnosis of aortic steno-sis is made Which of the following is consistent with that diagnosis?

a A decreased pulse pressure

b An increased arterial pressure

c A decreased left ventricular diastolic pressure

d An increased ejection fraction

e A decreased cardiac oxygen consumption

1-30. A 5-year-old Egyptian boy receives a sulfonamide antibiotic as phylaxis for recurrent urinary tract infections Although he was previouslyhealthy and well-nourished, he becomes progressively ill and presents toyour office with pallor and irritability A blood count shows that he isseverely anemic with jaundice due to hemolysis of red blood cells Which

pro-of the following is the simplest test for diagnosis?

a Northern blotting of red blood cell mRNA

b Enzyme assay of red blood cell hemolysate

c Western blotting of red blood cell hemolysates

d 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, andbronchiectasis He has had persistent infections and otitis media sincebirth A PA radiograph shows dextrocardia, and he has a negative saccha-rin test In the cross-section of the cilium shown below, which of the fol-lowing is primarily affected in this disorder?

breast-at 27 mmHg Which of the following trebreast-atment strbreast-ategies is mostappropriate?

a Administer alkali to treat metabolic acidosis

b Administer alkali to treat respiratory acidosis

c Decrease the respiratory rate to treat metabolic acidosis

d Decrease the respiratory rate to treat respiratory alkalosis

e Administer acid to treat metabolic alkalosis

1-34. A patient is sent to be examined by an endocrinologist after plaining of excessive thirst and increased excretion of urine The patient isthen referred to a neurologist and neuroradiologist, who detect the pres-ence 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 thesedeficits?

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 beenpresent 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 Physiologicalchanges that occur during pregnancy include which of the following?

a Decreased production of cortisol and corticosterone

b Increased conversion of glucose to glycogen

c Hypercapnia

d Increased hematocrit

e Reduced circulating gonadotropin levels

1-36. After a term uncomplicated gestation, normal delivery, and markable nursery stay, a 10-day-old female is readmitted to the hospitalbecause of poor feeding, weight loss, and rapid heart rate Antibiotics arestarted as a precaution against sepsis, and initial testing indicates anunusual echocardiogram with a very short PR interval and a large heart onx-ray Initial concern about a cardiac arrhythmia changes when a largetongue is noted, causing concern about glycogen storage disease type II(Pompe disease—232300—Table 3) Which of the following best explainswhy Pompe disease is more severe and lethal compared to other glycogenstorage diseases?

unre-a The deficiency is a degradative rather than synthetic enzyme

b The deficiency involves a liver enzyme

c The deficiency involves a lysosomal enzyme

d The deficiency causes associated neutropenia

e 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 numbnessand loss of balance, position, and vibratory sense in both of her lowerextremities Histologic examination of a smear made from a bone marrowaspiration reveals asynchrony in red blood cell precursors between thematuration of their nuclei and their cytoplasm Additional workup discov-ers achlorhydria, and a biopsy of the antrum of her stomach reveals chronicatrophic gastritis Which of the following is the most likely diagnosis?

1-38. An individual was admitted to the emergency room following loss ofconsciousness After the patient regained consciousness, he was examined

by a neurologist and presented with a right side hemiplegia, loss of tion on the left side of the face, and his ability to chew Which of the fol-lowing arteries was most likely subjected to an infarct that could accountfor the deficits described in this individual?

sensa-a Posterior inferior cerebellar artery

b Anterior inferior cerebellar artery

c Circumferential branches of basilar artery

d Paramedian branches of basilar artery

e Anterior spinal artery

1-39. A 34-year-old woman, who has been immobilized with a sprainedankle for the past 4 days, develops a throbbing pain that has spread to herentire left leg History reveals that she has been taking oral contraceptivesfor 15 years Compared to localized pain, such as one might experiencefrom a needle stick, which of the following is true of ischemic pain?

a Ischemic pain sensory fibers are classified as A delta (Ad) sensory fibers.

b Ischemic pain is produced by overstimulating somatic touch receptors.

c Ischemic pain is transmitted to the brain through the neospinothalamic tract.

d Ischemic pain receptors quickly adapt to a painful stimulus.

e 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

symp-toms subside Which of the following is the most effective noninvasive test

for the diagnosis of Helicobacter-associated gastric ulcers?

a Culture of stomach contents for H pylori

b Detection of H pylori antigen in stool

c Growth of H pylori from a stomach biopsy

d Growth of H pylori in the stool

e IgM antibodies to H pylori

1-41. A 26-year-old woman has rhinorrhea, excessive lacrimation, and ocularcongestion from a bout with the common cold Diphenhydramine providessymptomatic relief Which of the following is the most likely mechanism bywhich this drug gave symptom relief in the presence of this rhinovirus?

a α-Adrenergic activation (agonist)

b β-Adrenergic blockade

c Calcium channel blockade

d Histamine (H 1 ) receptor blockade

e Muscarinic receptor blockade

1-42. A pregnant 29-year-old woman diagnosed with type I diabetes 2decades ago, taking Humulin three times per day, is referred to the oph-thalmology clinic She is complaining of “floaters” and difficulty withnight-time driving Dilated indirect ophthalmoscopy coupled with biomi-croscopy and fundus photography detect the presence of proliferative dia-betic retinopathy with leaky retinal vessels indicative of increased vascularpermeability, growth of new, fragile vessels on the retina and posterior sur-face of the vitreous and macular edema Overexpression of fibronectin is ahistological marker of diabetic microangiopathy Which of the following isthe primary function of fibronectin in the basement membrane?

a Elasticity

b Cell attachment and adhesion

c Binding to selectins

d Binding to cadherins

e Binding to actin filaments

1-43. A 55-year-old male alcoholic presents with symptoms of liver ease and is found to have mildly elevated liver enzymes A liver biopsyexamined with a routine hematoxylin and eosin (H&E) stain reveals abnor-mal clear spaces in the cytoplasm of most of the hepatocytes Which of thefollowing materials is most likely forming these cytoplasmic spaces?

a Fatty acid synthase deficiency

1-45. A 2-week-old baby is hospitalized for inadequate feeding and poorgrowth The parents are concerned by the child’s weak cry An experiencedgrandmother accompanies them, saying she thought the cry sounded like

a cat’s meow The grandmother also states that the baby doesn’t look muchlike either parent The physician orders a karyotype after noting a smallhead size (microcephaly) and subtle abnormalities of the face Which of theresults pictured below is most likely?

1-46. A woman has severe irritable bowel syndrome characterized by quent, profuse, and symptomatic diarrhea She has not responded to first-line therapies and is started on alosetron Which of the following is themost worrisome adverse effect associated with this drug?

fre-a Cardiac arrhythmias (serious, e.g., ventricular fibrillation)

b Constipation, bowel impaction, ischemic colitis

c Parkinsonian extrapyramidal reactions

d Pulmonary fibrosis

e Renal failure

1-47. A patient with renal failure is undergoing periodic hemodialysiswhile awaiting a transplant Between dialysis sessions we want to reducethe body’s phosphate load by reducing dietary phosphate absorption andremoving some phosphate already in the blood Which of the followingdrugs would be most suitable for this purpose?

55-a Pleomorphic adenoma

b Ameloblastoma

c Mucoepidermoid carcinoma

d Adenoid cystic carcinoma

e Acinic cell carcinoma

1-49. A 24-year-old woman presents after having several “attacks” that lastfor about 24 h She states that during these attacks she develops nausea,vomiting, vertigo, and ringing in her ears Physical examination reveals asensorineural hearing loss Which of the following is the most likely cause

of this woman’s signs and symptoms?

a Acute suppurative inflammation of the middle ear

b Dilation of the cochlear duct and saccule

c Obstruction of the middle ear by a cyst filled with keratin

d Destruction of the tympanic membrane by a benign neoplasm

e 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 natal abnormalities, is being evaluated for possible visual problems He isnoted to have an abnormal white light reflex involving his right eye, andexamination finds a large mass that has almost completely filled the poste-rior chamber of this eye Which of the following cells are most likely to beseen proliferating in histologic sections from this mass?

pre-a Benign fibroblasts and endothelial cells

b Foamy macrophages with cytoplasmic clear vacuoles

c Plasmacytoid cells within a dense Congo red–positive stroma

d Small cells forming occasional rosette structures

e Spindle-shaped cells with cytoplasmic melanin

Block 2

Questions

2-1. Parents bring in their 2-week-old child fearful that he has ingested apoison They had delayed disposing one of the child’s diapers, and noted ablack discoloration where the urine had collected Later, they realized thatall 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 fol-lowing amino acid pathways are implicated in this phenomenon?

a The phenylalanine, tyrosine, and homogentisate pathway

b The histidine pathway

c The leucine, isoleucine, and valine pathway

d The methionine and homocystine pathway

e The arginine and citrulline pathway (urea cycle)

2-2. A 6-month-old boy is being evaluated for a lesion on his chin cal examination finds a raised, nontender, bright red strawberry-coloredvascular lesion measuring approximately 4 mm in greatest dimension Atthis time, which of the following is the best therapy for this infant?

Physi-a Leave alone and follow up on a routine basis

b Photocoagulation with yellow-green laser light

c Repeated injections with steroids

d Shave biopsy with frozen section diagnosis

e Wide local excision with sentinel node sampling

21

Copyright © 2008 by The McGraw-Hill Companies, Inc Click here for terms of use

2-3. A 52-year-old male develops an abscess following surgery to repair anabdominal gunshot wound Gram stain of the exudates from his foul-smelling abscess reveals numerous polymorphonuclear neutrophils (PMNs)and several gram-negative rods that did not grow on blood plates in thepresence of O2 Metabolism of O2 results in toxic reactive oxygen species.Which of the following enzymes is most likely involved in the followingreaction?

peri-a It will not permeate the membrane

b It can only cross the membrane through the lipid bilayer

c It causes water to flow across the membrane

d It is as diffusible through the membrane as water

e It is transported across the membrane by a carrier

symptoms including fever, malaise, and increasing respiratory problems Achest x-ray reveals enlarged hilar lymph nodes, while laboratory tests findher serum calcium level to be elevated A transbronchial biopsy revealsscattered chronic inflammatory cells, reactive epithelial changes, and sev-eral noncaseating granulomas The pathomechanism involved in the for-mation of these noncaseating granulomas involves the activation ofmacrophages to form epithelial cells by the action of which substance?

2-6. A nurse develops clinical symptoms consistent with hepatitis Sherecalls sticking herself with a needle approximately 4 months before, afterdrawing blood from a patient Serologic tests for HBsAg, antibodies toHBsAg, and hepatitis A virus (HAV) are all negative; however, she is posi-tive for IgM core antibody Which of the following characterizes the currenthealth state of the nurse?

a Does not have hepatitis B

b Has hepatitis A

c Has hepatitis C

d Is in the late stages of hepatitis B infection

e Is in the “window” (after the disappearance of HBsAg and before the ance of anti–HBsAg)

appear-2-7. A 10-year-old boy is brought into your office by his mother The boy issupporting 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 trippedover the curb and landed on the grass, catching himself with his hands Uponphysical 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 der has normal movement, but the boy is unwilling to lift his hand above hishead because it hurts Otherwise, hand and arm movements are relativelynormal with normal sensation You order an AP and lateral x-rays of the tho-rax and upper arm because you suspect which of the following?

shoul-a Colles’ fracture

b Scaphoid fracture

c Fracture of the surgical head of the humerus

d Dislocated sternoclavicular joint

e Greenstick fracture of the clavicle

2-8. A 65-year-old obese male presents with pain radiating down the left armand 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 LDHdoes suggest myocardial damage The managing physician knows that lactatedehydrogenase is composed of two different polypeptide chains arranged in theform of a tetramer Which of the following is the likely correlation between LDHmeasures 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 tohave a decrease in nerve conduction velocity and an X-linked mutation ofconnexin 32, consistent with Charcot-Marie-Tooth Disease Connexin is animportant component of which of the following?

a developing tumor along the rostral aspect of the medial wall of the lateralventricle Which of the structures in the illustration would be most likely tocontain this tumor?

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

2-12. A hospital worker is found to have hepatitis B surface antigen sequent tests reveal the presence of e antigen as well Which of the follow-ing best describes the worker?

Sub-a Is infective and has active hepatitis

b Is infective but does not have active hepatitis

c Is not infective

d Is evincing a biologic false-positive test for hepatitis

e Has both hepatitis B and hepatitis C

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

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, whichlasted 6 days She had no flu immunization during this period Her hemag-glutination inhibition (HI) antibody titer to swine flu virus was as follows:

(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 whenshe 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 thepediatrician feels an enlarged liver Initial blood tests show a mild acidosis (pH 7.2) with increased lactic acid and low blood glucose The Clinitest reac-tion is positive for reducing substances in the urine, but the glucose oxidasetest is negative for glucosuria A glycogen storage disease is suspected, and aliver biopsy dose shows mildly increased glycogen with marked cellular dam-age suggestive of early cirrhosis Assays for type IV glycogen storage diseaseare negative (Table 3), and the initial frozen urine sample is reanalyzed andfound to contain fructose The most likely diagnosis and the reasons for hypo-glycemia and glycogen accumulation is which of the following?

a Hereditary fructose intolerance with inhibition of liver phosphorylase

b Hereditary fructose intolerance with inhibition of glycogen synthase

c Essential fructosuria with inhibition of glycogen synthase

d Essential pentosuria with inhibition of liver phosphorylase

e Essential fructosuria with allosteric stimulation of glycogen synthase

2-17. A pregnant woman is found to have elevated blood pressure on hercheck-up at 8 months gestation, and testing by her obstetrician demon-

strates anemia with Hemolysis, Elevated Liver enzymes, and Low Platelets

that are characteristic of disease represented by the acronym HELLP drome The woman is hospitalized and fetal maturity tests are performedthat allow elective premature delivery The woman quickly recovers but thepremature newborn has a dilated heart and elevated liver enzymes that arecharacteristic of a defect in long chain fatty acid oxidation The potentialenzyme deficiencies are those responsible for sequential oxidation of fattyacids, which include which of the following?

syn-a Dehydrogenase, hydratase, dehydrogenase, thiolase

b Transacylase, synthase, reductase

c Hydratase, reductase, thioesterase

d Thioesterase, dehydrogenase, thiolase

e 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 ciency or loss of the carotid sinus reflex Which of the following is a com-ponent of this reflex?

defi-a Baroreceptor afferent fibers from cranial nerve XI

b Glossopharyngeal efferent fibers

c Interneurons within the nucleus ambiguus of the medulla

d Efferent fibers contained in the intermediate component of the facial nerve

e Vagal efferent fibers

2-19. A young couple comes to your urology office because of inability toconceive a wanted child after 1 year of unprotected sex The wife hadalready undergone a gynecological workup, including testing for 3 monthsshowing a normal ovulation profile as confirmed by an ovulatory kit Theprimary care physician describes the husband’s physical exam as normaland had already ordered a semen analysis and had forwarded the results toyou The semen volume was 0.5 mL, pH 6.8, and azospermic without anyfructose The husband has a brother, who has two children, one of whomhas confirmed cystic fibrosis You order a pelvic MRI of the husband todetermine whether which of the following exist(s)?

a Bilateral abdominal testicles

2-20. A 37-year-old obese man presents with signs and symptoms ofhyperglycemia After appropriate workup, he is diagnosed as having type IIdiabetes mellitus, which is due in part to insulin resistance Laboratoryevaluation of his serum also finds hypertriglyceridemia, which is due to hisdiabetes The most common type of secondary hyperlipidemia associatedwith diabetes mellitus is characterized by elevated serum levels of whichone of the following substances?

a Absence of the parafollicular cells

b Increased numbers of cells in the deep cortex of the lymph nodes

c Tetany

d Excess activity of osteoclasts

e Increased Ca 2+ levels in the blood

2-22. A 64-year-old male was admitted to the hospital with edema andcongestive heart failure He was found to have diastolic dysfunction char-acterized by inadequate filling of the heart during diastole The decrease inventricular filling is due to a decrease in ventricular muscle compliance.Which of the following proteins determines the normal stiffness of ventric-ular muscle?

2-23. A family routinely consumed unpasteurized milk, claiming “bettertaste.” Several members experienced a sudden onset of crampy abdominal

pain, fever, and bloody, profuse diarrhea C jejuni was isolated and

identi-fied from all patients Which of the following is the treatment of choice forthis type of enterocolitis?

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 tors, implying a 75–100% risk for eventual hypertension in mother and a 5–10% risk to offspring

fac-d Multifactorial determination results from multiple pre- and postnatal mental factors, implying a 75–100% risk for eventual hypertension in mother and a 5–10% risk to offspring

environ-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 heartfailure Her condition rapidly deteriorates and she dies in heart failure Atautopsy, patchy interstitial infiltrates composed mainly of lymphocytes arefound, some of which surround individual myocytes Which of the follow-ing is the most likely cause of this patient’s heart failure?