UWorld Test Reviews 2

Question 1

explain the mechanism of exercise-induced hypoglycemia in patients with diabetes mellitus

Answer 1

translocation of GLUT4 is induced by muscle contraction, allowing insulin-independent glucose uptake during exercise

patients with diabetes lack physiologic insulin regulation; therefore, they experience rapid uptake of glucose while exercising…

…As blood glucose levels fall, glucagon/epinephrine rise, causing palpitations/sweating, which are relived by intake of sugar

Question 2

which of the following describes how HIV lays dormant?
a. genomically integrated viral DNA from lymphoid tissue
b. persistent extrachromosomal viral DNA from B lymphocytes
c. preassembled viral particles from circulating CD4+ lymphocytes

Answer 2

a. genomically integrated viral DNA from lymphoid tissue - accomplished via intergrase during early stages of infection

majority of HIV resides in lymphoid tissues - lymph nodes, lymphatic vasculature, GALT/MALT; can also reside in CNS (astrocytes, microglia) and lungs (alveolar macrophages)

[latency is NOT CD4+ T cells - these are short lived cells]

Question 3

what are the following therapies used for? include how they work:
a. infliximab
b. rituximab
c. interleukin-2
d. imatinib
e. abciximab

Answer 3

a. infliximab = IgG1 mAb to TNF-alpha; treats rheumatoid arthritis, ankylosing spondylitis, Crohn’s

b. rituximab = mAb to CD20 (B cell); treats B cell lymphomas

c. interleukin-2 = cytokine that activates T cells; treats renal cell carcinoma and melanoma

d. imatinib = small molecule inhibitor of BCR/ABL protein tyrosine kinase; treats CML (Philadelphia chromosome)

e. abciximab = chimeric mouse-human mAb to GP IIb/IIIa receptor (blocks platelet aggregation); used during angioplasty

Question 4

mediastinal mass staining positive for chromogranin =

Answer 4

small cell lung cancer: associated with smoking, centrally located

histology shows small round/oval cells with scant cytoplasm, hyperchromatic (blue) nuclei, and granular chromatin

Question 5

which diuretics act at the following sites:
a. PCT
b. descending limb of Henle
c. thick ascending loop of Henle
d. DCT
e. collecting duct

Answer 5

a. PCT: carbonic anhydrase (acetazolamide)

b. descending limb of Henle: osmotic diuretics (mannitol)

c. thick ascending loop of Henle: loop diuretics (furosemide)

d. DCT: thiazide diuretics (hydrochlorothiazide)

e. collecting duct: K+ sparing diuretics = Na+ channel blockers (amiloride) + aldosterone receptor antagonists (spironolactone)

Question 6

A patient is taking diuretics for heart failure which are causing muscle weakness and cramping. This is most likely a ______ diuretic.

To help prevent this effect, a ______ diuretic is added because…

Answer 6

A patient is taking diuretics for heart failure which are causing muscle weakness and cramping. This is most likely a LOOP diuretic (FUROSEMIDE) - these treat symptoms of HF like dyspnea and edema.

To help prevent this effect, a K+ SPARING DIURETIC diuretic is added because… all diuretics except potassium sparing class cause K+ loss by increasing Na+ delivery to the late distal tubule/collecting duct

K+ sparing diuretics include those that block ENaC (amiloride, triamterene) and those that inhibit aldosterone receptor (spironolactone, eplerenone)

Question 7

young child with bilateral sensorineural hearing loss + prolonged QT interval = defect in what? What is this disease called?

Answer 7

Jervell and Lange-Nielsen syndrome: AR disorder due to defect in voltage-gated potassium channels

—> bilateral sensorineural hearing loss + congenital long QT syndrome (predisposes to ventricular arrhythmias and sudden cardiac death)

Question 8

which skin lesions do the following statements describe?
a. acantholysis and multinucleated giant epithelial cells
b. epidermal hyperplasia and cytoplasmic vacuolization
c. subcorneal bacterial collection and neutrophilic infiltration
d. subepidermal linear complement deposits and separation

Answer 8

a. acantholysis and multinucleated giant epithelial cells = herpes simplex labialis

b. epidermal hyperplasia [acanthosis] and cytoplasmic vacuolization [koilocytes] = verruca vulgaris (cutaneous wart), caused by HPV

c. subcorneal bacterial collection and neutrophilic infiltration = impetigo

d. subepidermal linear complement deposits and separation = bullous pemphigoid (Abs against hemidesmosomes)

Question 9

place the following in order of FASTEST conductance to SLOWEST conductance: atrial muscle, ventricular muscle, Purkinje system, AV node

Answer 9

Park AT VENTure AVenue:
Purkinje > Atrial muscle > Ventricular muscle > AV node

note AV node is slowest to allow for delay so ventricles can completely fill

note Purkinje fibers are the fastest because they have to reach all the way around the ventricles

and atrial is faster than ventricle so A before V

Question 10

cause and presentation of oculocutaenous albinism

Answer 10

cause: AR defect in tyrosinase, which converts tyrosine to DOPA as first step in melanin production

presentation: photophobia, decreased visual acuity (underdeveloped optic nerve + absent foveae), translucent iris, strabismus/nystagmus, white skin/hair, high risk of skin cancer (squamous cell)

Question 11

how are the following affected by subacute (granulomatous, de Quervain) thyroiditis?
a. thyroid hormone levels
b. thyroglobulin levels
c. TSH levels
d. radioactive uptake

Answer 11

viral infection causes cross-reaction, activation of cytotoxic T cells causing destruction of thyroid follicles —>

a. thyroid hormone levels - ELEVATED, due to release of preformed hormone

b. thyroglobulin levels - ELEVATED, due to release of preformed thyroglobulin

c. TSH levels - LOW, due to negative feedback

d. radioactive uptake - LOW, reflecting decreased thyroid activity due to loss of TSH stimulation

Question 12

which of the following infectious agents can cause cold agglutinins?
a. Legionella pneumophila
b. Mycobacterium kansasii
c. Mycoplasma pneumoniae
d. Streptococcus pneumoniae

Answer 12

c. Mycoplasma pneumoniae

cold agglutinins: cross-reactive IgM Abs that attach to RBC and activate complement, inducing erythrocyte lysis

bind at COLD temps (while warm agglutinins bind at warm temps!)

may cause intravascular hemolysis (while warm agglutinins cause extravascular hemolysis!)

Question 13

what is the strongest risk factor for ectopic pregnancy?

Answer 13

prior pelvic surgery !

Question 14

child with tremors and seizures + musty body odor + light skin/eye color =

Answer 14

phenylketonuria (PKU): AR deficiency of phenylalanine hydroxylase, which catalyzes conversion of phenylalanine to tyrosine

excess phenylalanine —> irreversible neurological injury
phenylalanine metabolites —> musty odor
low tyrosine —> reduced melanin, light pigmentation

Question 15

state the hereditary pattern of the following genetic diseases:
a. classic galactosemia
b. hemophilia B
c. Huntington’s
d. Rett syndrome
e. Leber hereditary optic neuropathy

Answer 15

a. classic galactosemia = AR
b. hemophilia B = XLR (males)
c. Huntington’s = AD
d. Rett syndrome = XLD (females)
e. Leber hereditary optic neuropathy = mitochondrial (maternal transmission only)

Question 16

which of the following ECG changes occur with exercise?
a. ST segment depression
b. QT interval elongation
c. T wave inversion
d. QRS complex narrowing
e. PR interval shortening

Answer 16

e. PR interval shortening

beta1 —> increased HR and contractility… this occurs via more frequent initiation of impulses (more frequent P waves) in SA node and increased conduction velocity from atria to ventricles (shortened PR interval) in AV node

all together, this = sinus tachycardia

Question 17

bilateral ligation of which of the following arteries is the method of controlling severe postpartum hemorrhage due to failure of uterine atony?
a. common iliac
b. external iliac
c. internal iliac
d. internal pudendal
e. ovarian

Answer 17

c. internal iliac - main blood supply to the pelvis

the main blood supply to the uterus is the uterine artery (which comes off internal iliac), but there are robust collaterals

Question 18

what type of vaginitis do the following indicate:
a. thin, off-white discharge with fishy odor + Clue cells and positive whiff test
b. thin, yellow-green malodorous, frothy discharge + vaginal inflammation
c. thick, cottage cheese discharge + vaginal inflammation

Answer 18

a. thin, off-white discharge with fishy odor + Clue cells and positive whiff test = Gardnerella vaginalis (bacterial vaginosis) [Clue cell = vaginal squamous epithelial cell covered with many small G. vaginalis organisms]

b. thin, yellow-green malodorous, frothy discharge + vaginal inflammation = Trichomonas vaginalis (trichomoniasis)

c. thick, cottage cheese discharge + vaginal inflammation = Candida albicans (candida vaginitis)

Question 19

describe the blood supply to the ureter - how is this relevant in transplant operations?

Answer 19

proximal ureter is supplied by branches of renal artery, while distal ureter is supplied by superior vesical artery, and in between it is anastomotic and variable

in kidney transplant, donor kidney is placed retroperitoneally in the right iliac fossa (native kidneys left in place), and blood supply is established by anastomosing the donor renal artery with the recipient external iliac artery, while the proximal 1/3 of donor ureter is connected to recipient bladder… distal ureteral ischemia is a known risk due to lack of anastomotic connections

Question 20

64yo pt presents with 3 days of diarrhea occurring after eating chicken salad. Pt has had 4-6 episodes of diarrhea per day with no blood in stool. Pt takes TNF inhibitor for psoriatic arthritis and proton pump inhibitor for gastritis. Cultures of stool yield gram neg. bacilli that are non-lactose fermenting and oxidase negative. Which of the following is the most likely complication associated with this patient’s current infection?
a. chronic malabsorption
b. generalized seizure
c. Guillain-Barre
d. hemolytic uremic syndrome
e. osteomyelitis

Answer 20

e. osteomyelitis

pt contracted non-typhoidal salmonella from poultry/eggs, exotic pet contact

ingested Salmonella must survive acidic stomach to reach small intestine - patients taking proton pump inhibitors require smaller infectious doses

invasive disease more likely in immunocompromised patients - osteomyelitis more common in patients with sickle cell disease

Question 21

19yo M comes to office due to eye pain and blurry vision in both eyes in last several days. Sustained open globe injury to R eye 3mo ago due to altercation. He was treated with surgical repair and prophylactic antibiotics. The L eye was unaffected. Today, there is bilateral conjunctival injection and decreased visual acuity in both eyes. Vitreous samples reveal multinucleated giant cells. Which of the following is the most likely mechanism of this presentation?
a. granulomatous response to reactivation of latent viral infection
b. mixed inflammatory reaction triggered by GI pathogen
c. neutrophilic response to intraocular infection
d. T-cell response to previously sequestered antigen
e. Type IV hypersensitivity reaction to an antibiotic

Answer 21

d. T-cell response to previously sequestered antigen

this is because eye is area of immune privilege - antigens were released into lymphatic system via trauma, causing T cells to mount immune response

Question 22

multiple seemingly unrelated phenotypic manifestations (often in different organ systems) as a result of a single genetic defect

Answer 22

pleiotropy

Question 23

Pierre Robin sequence

Answer 23

sequence = single developmental defect which causes a cascade of additional malformations

Pierre Robin sequence: hypoplasia of mandibular prominence leads to micrognathia, which causes posterior displacement of tongue (glossoptosis), which blocks fusion of palatine shelves, resulting in U-shaped cleft palate, which causes difficulty breathing because the tongue prolapses into the posterior oropharynx (breathing improves when patient is prone)

Question 24

autopsy of lung reveals alveolar macrophages containing aggregates of golden-brown cytoplasmic granules that turn dark blue with Prussian blue staining - what does this mean?

Answer 24

Prussian blue staining detects ferric iron stores (ferritin, hemosiderin)

macrophages containing golden-brown cytoplasmic granules that turn blue with Prussian blue staining = hemosiderin-laden macrophages (siderophages), in lung these are ”heart failure cells”

Question 25

Chest x-ray of 24yo pt shows patchy, interstitial infiltrates. Sputum gram stain shows numerous leukocytes but no organisms. Which of the following is the best initial treatment: a. antagonist of folate metabolism b. inhibitor of bacterial cell wall synthesis c. inhibitor of bacterial protein synthesis d. inhibitor of ergosterol synthesis e. inhibitor of mycolic acid synthesis

Answer 25

c. inhibitor of bacterial protein synthesis likely has “walking pneumonia” (form of atypical pneumonia) caused by *Mycoplasma pneumoniae* or *Chlamydia pneumoniae* do not have peptidoglycan cell walls - Mycoplasma has NO cell wall, Chlamydia has cell wall of alternative protein —> cannot be gram stained treatment requires *macrolide or tetracycline* (bacterial protein synthesis inhibitor) because it’s ineffective to use beta-lactams [Legionella pneumophilia also causes atypical pneumoniae but is usually associated with GI symptoms and more severe clinical illness + lobar infiltrate on CXR] [mycolic acid = mycobacterium, aka TB]

Question 26

how do Vitamin D analogs treat psoriasis?

Answer 26

Vitamin D analogs (calcipotriene, calcitriol) activate Vit. D receptor, which is a *nuclear transcription factor* —> *inhibition of T-cell and keratinocyte proliferation + stimulate differentiation*

Question 27

which of the following is the best initial pharmacotherapy for diabetic neuropathy (distal symmetric polyneuropathy)? a. amitriptyline b. clonazepam c. fluoxetine d. naproxen e. pyridoxine

Answer 27

a. amitriptyline: tricyclic antidepressant, blocks excitatory NMDA receptors in spinal cord can also treat with serotonin-NE reuptake inhibitor (duloxetine, venlafaxine), gabapentinoid (pregabalin, gabapentin)

Question 28

what is the purpose of the metyrapone stimulation test?

Answer 28

sensitive indicator of HPA axis integrity (hypothalamic pituitary adrenal) - *metyrapone blocks cortisol synthesis* via inhibition of 11-beta-hydroxylase (converts 11-deoxycortisol to cortisol in zona fasciculata) —> reduction in cortisol stimulates increase in pituitary ACTH secretion this causes increased production of 11-deoxycortisol, which is metabolized in liver to 17-hydroxycorticosteroids that accumulate in liver… failure of these to rise implies primary or secondary adrenal insufficiency (distinguished based on plasma ACTH levels)

Question 29

which of the following is an example of reciprocal induction signaling during embryological development? a. endoderm and splanchnic mesoderm during vasculogenesis b. metanephric blastema and ureteric bud during kidney formation c. neural crest and endoderm during gut tubulogenesis d. Sertoli cells and primordial germ cells during gamete development

Answer 29

b. metanephric blastema and ureteric bud during kidney formation reciprocal induction = both tissues must be present to induce normal development in each other metanephric blastema induces formation of ureteric bud, which induces metanephric blastema to condense and epithelialize… which then induces ureteric bud to branch/elongate

Question 30

couple is asking about genetic risk of CF for their child. She is from a small city with a stable population, where carrier frequency of CF is 1/30. He is from nearby community, where carrier frequency is 1/100. What is the probability of disease in the child? (both parents are healthy)

Answer 30

Cystic fibrosis is AR, so both parents must be a carrier… if both are carriers, 1/2 chance EACH that they pass the mutant allele P(affected child) = 1/30 x 1/100 x 2(1/2) = 1/12,000

Question 31

where in the cell does heme synthesis occur?

Answer 31

partly in mitochondria, partly in cytoplasm note ALAS and ferrochelatase (protoporphyrin —> heme) function in the mitochondria ALAD and PBG deaminase function in cytoplasm

Question 32

white plaque-like oral lesions which can be easily scarped off, revealing erythematous mucosa underneath + enlarged cervical and axillary lymph nodes =

Answer 32

this describes *thrush* caused by *Candida albicans* note leukoplakia (hyperplasia of squamous mucosa, can evolve into dysplasia/carcinoma) appears similarly but cannot be easily scraped off

Question 33

which clotting factors are produced in the liver and would therefore be functionally deficient in a patient with liver disease?

Answer 33

clotting factors II, VII, IX, X are produced in liver and activated by vitamin-K-dependent carboxylation note factor VII has the shortest half life and will be most affected

Question 34

which of the following will be increased by inhaled anesthetics? a. GFR b. effective renal plasma flow c. LV EF d. hepatic blood flow e. cerebral blood flow

Answer 34

e. cerebral blood flow - due to decreased vascular resistance; undesirable effect than increases ICP all other parameters decrease

Question 35

congenital QT prolongation is due to mutation in what?

Answer 35

mutated membrane K+ channel proteins —> prolonged cardiac myocyte action potential patients are predisposed to torsades de pointes (ventricular tachyarrhythmia)

Question 36

what is the cause of a branchial cleft cyst?

Answer 36

lateral neck mass anterior to sternocleidomastoid muscle - results from incomplete involution of the 2nd pharyngeal *cleft* [NOT a pouch malformation]

Question 37

what is the structure of MHC I vs MHC II

Answer 37

MHC I: heavy chain + beta2 microglobulin (present on all nucleated cells, present to CD8+) MHC II: alpha + beta polypeptide chains (present on APC, present to CD4+)

Question 38

Histology of patient’s tissue reveals defect affecting a large extracellular glycoprotein, which is normally found abundantly in large blood vessels, periosteum, and zonular fibers of the lens. It functions to form microfibrils by surrounding elastin. What protein is this, and what genetic disorder does this describe?

Answer 38

*Marfan syndrome*: defect in *fibillin-1*, a major component of microfibrils that form a sheath around elastin fibers —> long arms, scoliosis/kyphosis, ectopia lentis, aortic dilation/ regurgitation/ dissection, mitral valve prolapse, spontaneous pneumothorax (apical blebs), inguinal hernias, skin striae

Question 39

Patient presents with bloody diarrhea. Sigmoidoscopy with biopsy reveals colonic ulcers with undermining edges containing trophozoites. Patient recently returned from trip to Egypt. What is the most likely pathogen?

Answer 39

*Entamoeba histolytica*: fecal-oral (contaminated food/water), developing nations —> colitis (diarrhea, blood stool with mucus) —> liver abscess (RUQ pain + fever) —> brain, lung, pleura abscess (less common) dx confirmed when cysts and trophozoites are seen in stool or biopsy shows flask-shaped ulcers (with trophozoites)

Question 40

what is responsible for the green color of pus and sputum in bacterial lung infections?

Answer 40

neutrophil *myeloperoxidase*: blue-green heme-based pigmented molecules, contained within *azurophilic granules* (note the name!) catalyzes production of HCl during phagocytic respiratory burst

Question 41

child with persistent ulcerated facial ulcer (2 months) has extreme sensitivity to sunlight (develops freckles). skin in sun-exposed areas is dry/rough with erythematous macules. Biopsy of facial ulcer reveals squamous cell carcinoma. A defect in which enzyme is most likely responsible for this patient’s condition? a. 3’—>5’ exonuclease b. DNA ligase c. endonuclease d. helicase e. topoisomerase

Answer 41

c. endonuclease dx: xeroderma pigmentosum: AR defect in nucleotide excision repair (for thymine dimers) recall thymine dimers are repaired via UV-specific endonuclease

Question 42

pt presents with severe sore throat and difficulty swallowing. PE shows pharyngeal erythema + coalescing, gray exudate. bilateral cervical lymph node enlargement/tenderness. swab shows non-spore-forming Gram+ rods. which of the following is helpful in preventing systemic complications of this infection? a. airway edema reduction with inhaled epinephrine b. antibiotics to kill bacteria in bloodstream c. blunting immune response with glucocorticoids d. preformed antibodies administration to bind bacterial product e. vaccination with inactivated bacterial toxin

Answer 42

d. preformed antibodies administration to bind bacterial product dx: *Corynebacterium diphtheriae*: diphtheriae toxin inhibits host ADP-ribosylation of EF-2 systemic - myocarditis/heart failure, neurologic toxicity risk factors - inadequate vaccination/ lack of 10-year booster shot (otherwise rare in resource-rich countries)

Question 43

stridor + drooping + “tripod” position in child =

Answer 43

epiglottitis: caused by *Haemophilus influenzae* type B, occurs in unvaccinated individuals

Question 44

adolescent with fluctuating tingling/numbness in R shoulder, arm, hand. recently developed dull pain in R little finger and hand. Symptoms worsen with overhead activities and when throwing. Pt has extra rib. PE shows R-sided weakness of intrinsic hand muscles. Which muscle is contributing to this patient’s condition? a. coracobrachialis b. scalenes c. subscapularis d. teres minor e. triceps brachii

Answer 44

b. scalenes dx: thoracic outlet syndrome: compression of brachial plexus between first rib and clavicle, within scalene triangle

Question 45

pt with mild hypercalcemia which runs in the family. labs show slightly elevated PTH, very low urinary Ca2+ levels, and normal 25-hydroxyvitamin D level. A mutation in which of the following receptors is most likely responsible? a. intracellular receptor with DNA-binding domain b. membrane-bound receptor coupled with G protein c. transmembrane ligand-gated ion channel d. transmembrane receptor associated with intrinsic tyrosine kinase activity e. transmembrane receptor causing activation of Janus kinase/STAT pathway

Answer 45

b. membrane-bound receptor coupled with G protein dx: *familial hypocalciuric hypercalcemia* (AD) due to mutation of calcium-sensing receptors (CaSRs) - transmembrane Gq coupled (metabotropic) required for neg. feedback of PTH

Question 46

F pt w/ primary amenorrhea + pelvic and crampy lower abdominal pain recurring monthly and resolving after a couple days + normal secondary sexual characteristics + palpable mass anterior to the rectum =

Answer 46

imperforate hymen: pain from blood accumulating behind the hymen, causes increasing pressure on pelvic organs (defecatory/urinary dysfunction) exam reveals smooth vaginal bulge (hematocolpos) and palpable mass anterior to rectum (distended vagina)

Question 47

at what week do each of the following occur? a. blastocyst implantation b. gastrulation c. intestinal fixation to abdominal wall d. neural crest migration e. primitive alveoli formation

Answer 47

a. blastocyst implantation = week 1 b. gastrulation = week 3 c. intestinal fixation to abdominal wall = weeks 10-12 d. neural crest migration = week 5 e. primitive alveoli formation = week 26 (saccular stage), alveoli continue to mature after birth

Question 48

67 y/o M pt with recurrent episodes of syncope while shaving + normal cardiac exam =

Answer 48

*carotid hypersensitivity*: type of reflex syncope, caused by tactile stimulation of carotid sinus while standing —> exaggerated vasovagal response causes marked peripheral vasodilation (—> decreased SVR) risk factors: advanced age, carotid atherosclerosis

Question 49

which of the following viruses undergoes genetic shift, similar to influenza? a. Hep C b. HPV c. measles d. polio e. rotavirus

Answer 49

genetic shift = *reassortment* of genomic segments of human with animal strain e. rotavirus - requires a segmented genome segmented viruses: orthomyxovirus, reovirus (includes rotavirus), bunyavirus, arenavirus

Question 50

what are 3 signs (lab levels) of classic complement pathway activation? what is the most common cause of complement deficiency?

Answer 50

low C3 and C4 + normal factor B most common cause of complement deficiency is autoantibodies - activate classical pathway after binding host antigens

Question 51

T/F: Fc portions of all antibody types (IgG, IgA, IgE, IgD, IgM) can activate complement system

Answer 51

FALSE - only IgG and IgM can activate compliment !

Question 52

which complement pathway does this describe: “auto-activation of C3 component”

Answer 52

auto-activation of C3b triggers *alternative complement* pathway labs show normal C4, low C3, low factor B

Question 53

acute facial flushing following overdose of vitamins is most likely due to a vitamin which has which of the following functions? a. coenzyme for transketolase b. coenzyme in hydroxylation of prolyl and lysyl residues c. component of coenzyme A d. precursor for flavin adenine dinucleotide production e. precursor for nicotinamide adenine dinucleotide production

Answer 53

acute facial flushing = *niacin (B3)* toxicity … e. precursor for nicotinamide adenine dinucleotide (NAD, also NADPH) production recall niacin supplementation is effective in treatment of hyperlipidemia - at high doses, niacin increases activity of lipoprotein lipase (LPL)

Question 54

which vitamins are these? a. coenzyme for transketolase b. coenzyme in hydroxylation of prolyl and lysyl residues c. component of coenzyme A d. precursor for flavin adenine dinucleotide production e. precursor for nicotinamide adenine dinucleotide production

Answer 54

a. coenzyme for transketolase (PPP) = *thiamine (B1)* b. coenzyme in hydroxylation of prolyl and lysyl residues = *vitamin C* c. component of coenzyme A (acetylation rxns) = *pantothenic acid (B5)* d. precursor for flavin adenine dinucleotide (FAD) production = *riboflavin (B2)* e. precursor for nicotinamide adenine dinucleotide (NAD, also NADPH) production = *niacin (B3)*

Question 55

what toxicities are associated with the following vitamins? a. thiamine (B1) b. Vitamin C c. pantothenic acid (B5) d. riboflavin (B2) e. niacin (B3)

Answer 55

a. thiamine (B1) - none! b. Vitamin C - kidney stones, false-negative stool guaiac results (?) c. pantothenic acid (B5) - none! d. riboflavin (B2) - none! e. niacin (B3) - increased prostaglandin production, causing cutaneous vasodilation, flushing, pruritus

Question 56

contrast presentation of primary somatosensory cortex to that of thalamus

Answer 56

both can cause pure sensory deficit; however, lesions to primary somatosensory cortex will cause sensory loss based on somatotopic organization (will not effect all parts equally), while lesions to thalamus will cause complete contralateral sensory loss (spinothalamic tract + dorsal columns —> ventral posterior lateral/VPL; trigeminal —> ventral posterior medial/ VPM)

Question 57

which sensory tracts provide input to the VPL vs VPM of thalamus?

Answer 57

spinothalamic tract + dorsal columns —> ventral posterior lateral/VPL trigeminal —> ventral posterior medial/ VPM

Question 58

in adults, the main response to hypoxemia is coordinated by…. [organ]

Answer 58

*kidneys* - peritubular fibroblasts in the renal cortex sense hypoxia using TF *hypoxia inducible factor 1-alpha (HIF-1alpha)* when O2 is available, HIF-1alpha is marked for proteasomal degradation when O2 is low, HIF-1alpha accumulates and increases EPO production

Question 59

how is priapism treated?

Answer 59

aka painful, firm erection tx: *alpha agonist* (phenylephrine) - induces contraction of cavernous smooth muscle to reduce venous obstruction by the engorged corpora recall flaccid state maintained by tonic sympathetic activity; erection caused by PNS activation

Question 60

18mo M being evaluated for gradual regression of developmental milestones that began at 5 months. Weight and height are below 5th percentile. PE shows enlarged liver and spleen, diminished deep tendon reflexes in all limbs, and hypotonia. Funduscopy shows a cherry red spot. The patient most likely has accumulation of what?

Answer 60

**sphingomyelin** dx: *Niemann-Pick*: AR deficiency in sphingomyelinase, common in Ashkenazi Jews sphingomyelin accumulates in macrophages (“foam cells”), which accumulate in liver, spleen, CNS, retina

Question 61

tumor biopsy stains positive for cytokeratin - what type of proteins are these and what type of cell is most likely the origin of the tumor?

Answer 61

cytokeratins = intermediate filaments found in epithelial cells

Question 62

4yo presents with 3 day history of diarrhea which began watery but has now become bloody. Stool cultures grow non-lactose fermenting, gram neg. rods on MacConkey agar. Bacteria ferment glucose without gas-production, do not generate hydrogen sulfide when grown on triple sugar iron agar, and cannot replicate at refrigeration temperatures. Which pathogen is the causative agent?

Answer 62

Shigella - causes invasive dysentery (blood diarrhea) invades M (microfold) cells of Peyer’s patches, lyses its containment vacuole, multiples in cytoplasm, spreads via host cell active polymerization

Question 63

what is the mechanism of the following HIV drugs? a. atazanavir b. efavirenz c. enfuvirtide d. maraviroc e. raltegravir f. tenofovir

Answer 63

a. atazanavir: protease inhibitor (prevent cleavage of HIV polyproteins) b. efavirenz: non-nucleoside RT inhibitor (bind allosterically) c. enfuvirtide: fusion inhibitor (binds GP41) d. maraviroc: CCR5 (chemokine coreceptor 5) inhibitor e. raltegravir: integrase inhibitor f. tenofovir: non-nucleoside RT inhibitor (bind allosterically)

Question 64

64yo M w/ Type 2 diabetes mellitus is evaluated for occasional dizziness which usually occurs while playing table tennis. Pt has had no falls or LOC. No known history of coronary artery disease or stroke. ECG shows normal sinus rhythm. Doppler ultrasound of L vertebral artery shows retrograde (caudal) flow. Which artery is most likely occluded?

Answer 64

left subclavian dx: *subclavian steal syndrome*: typically due to stenosis of subclavian artery proximal to origin of vertebral artery - lowered distal subclavian artery pressure causes reversal of blood flow (“steal”) from contralateral vertebral artery to ipsilateral vertebral artery, away from brainstem (—> dizziness)

Question 65

Woman presents for evaluation of genital warts. Pt has occasional pruritus but no pain. Pt is sexually active. Exam shows several verrucous, skin-colored lesions over the labia majora. The virus involved also has affinity for which of the following? a. alveoli b. false vocal cords c. paranasal sinuses d. trachea e. true vocal cords

Answer 65

e. true vocal cords dx: HPV (dsDNA) - types 6 and 11 cause warts HPV has predilection for *stratified squamous epithelium*… in respiratory tract, only true vocal cords are covered with stratified squamous [false vocal cords = ventricular folds, mucous membrane lined in respiratory epithelium - ciliated, pseudostratified columnar —> lubricate true vocal cords]

Question 66

a mutation in the Fas gene product would result in a defect in which of the following immunologic mechanisms? a. activation-induced T lymphocyte death b. affinity maturation of B lymphocytes c. clonal anergy of T lymphocytes d. Th1 and Th2 lymphocyte differentiation

Answer 66

a. activation-induced T lymphocyte death cytotoxic T cells trigger apoptosis by activating Fas receptors (in TNF receptor family) —> initiation of extrinsic apoptotic pathway (via FADD —> caspase 8/10 —> caspase 3/6)

Question 67

Pt has microcytic, hypochromic anemia that does not respond to iron therapy. Symptoms improve with pyridoxine (B6) supplementation. What enzyme is affected by this condition?

Answer 67

dx: X-linked sideroblastic anemia - due to defective **5-aminolevulinate synthase**, for which B6 is a cofactor this enzyme is first/ rate-limiting step in porphyrin synthesis (glycine + succinyl CoA —> aminolevulinic acid)

Question 68

which of the following drugs would best provide symptomatic improvement of moderate peripheral arterial disease due to direct dilation of arteries and inhibition of platelet aggregation? a. abciximab b. argatroban c. aspirin d. cilostazol e. heparin f. tissue plasminogen activator g. warfarin

Answer 68

d. **cilostazol**: inhibits platelet phosphodiesterase (which breaks down cAMP —> PKA inhibits platelet aggregation) + direct arterial vasodilator a. abciximab = mAb to platelet IIb/IIIa receptor b. argatroban = direct thrombin inhibitor (used in heparin-induced thrombocytopenia) c. aspirin = irreversible COX1/2 inhibitor used for secondary prevention (does not improve PAD symptoms) e. heparin = activates antithrombin III f. tissue plasminogen activator (aka alteplase) = converts plasminogen to plasmin to cause fibrinolysis g. warfarin = competitive inhibitor of vit. K epoxide reductase (reduces production of factors II, VII, IX, X, C, S)

Question 69

what is the MOA of the following drugs: a. abciximab b. argatroban c. aspirin d. cilostazol e. heparin f. tissue plasminogen activator g. warfarin

Answer 69

a. **abciximab** = mAb to platelet IIb/IIIa receptor b. **argatroban** = direct thrombin inhibitor (used in heparin-induced thrombocytopenia) c. **aspirin** = irreversible COX1/2 inhibitor used for secondary prevention d. **cilostazol**: inhibits platelet phosphodiesterase (which breaks down cAMP —> PKA inhibits platelet aggregation) + direct arterial vasodilator e. **heparin** = activates antithrombin III f. **tissue plasminogen activator** (aka alteplase) = converts plasminogen to plasmin to cause fibrinolysis g. **warfarin** = competitive inhibitor of vit. K epoxide reductase (reduces production of factors II, VII, IX, X, C, S)

Question 70

Patient with puncture wound through R cubital fossa has decreased sensation in the lateral palm, inability to flex proximal interphalangeal joint, and inability to pronate the forearm. Which of the following arteries was also most likely injured? a. anterior interosseous artery b. brachial artery c. deep brachial artery d. radial artery e. radial recurrent artery f. ulnar artery

Answer 70

b. *brachial artery* - runs adjacent to median nerve in cubital fossa dx: median nerve injury - impairment of forearm pronation (pronator teres) and proximal interphalangeal joint flexion (flexor digitorum superficialis) + sensory deficits

Question 71

what is reverse T3 (rT3)?

Answer 71

inactive form of thyroid hormone that is generated almost entirely from peripheral conversion of T4

Question 72

Pt is 21yo M presenting with impaired balance, tremor, and difficulty speaking. Symptoms have developed slowly over last several months. Pt has elevated serum transaminases. Viral hepatitis serologies are negative. He has a sibling who was diagnosed at a young age with progressive neurological disease. Which of the following diagnostic studies would be most helpful? a. anti-smooth muscle antibodies b. genetic testing for triplet repeat expansions c. MRI of brain d. serum alpha-1 antitrypsin levels e. slit lamp examination

Answer 72

e. *slit lamp examination* to detect *Kayser-Fleischer rings* dx: **Wilson disease**: AR mutation in ATP7B intracellular hepatocyte copper transport gene —> reduced formation of *ceruloplasmin* (extracellular copper transport protein) and decreased secretion of copper into biliary system presents in young adults with liver disease + neuropsychiatric symptoms + Kayser-Fleischer rings tx: chelators (D-penicillamine, trientine) + *zinc* (interferes w/ copper absorption)

Question 73

patient who smells something strange then has a seizure = seizure where?

Answer 73

olfactory hallucination is a classic aura of *temporal lobe epilepsy*

Question 74

32yo F experience is double vision, heaviness in eyelids, and weakness in hands that worsens throughout the day. X-ray shows anterior mediastinal mass. The mass originates from an organ that is derived from a pharyngeal pouch. Which of the following most directly originates from the same pouch? a. inferior parathyroid glands. b. Larynx c. Palatine tonsils. d. Superior parathyroid glands. e. Thyroid gland.

Answer 74

a. *inferior parathyroid glands* = 3rd pouch [dx = myasthenia gravis, mass is an associated thymoma] b. Larynx = 4th + 6th pouches c. Palatine tonsils = 2nd pouch d. Superior parathyroid glands = 4th pouch e. Thyroid gland - follicular cells from 1st/2nd (outpouching of pharynx), parafollicular C cells from 4th pouch

Question 75

what are the following drugs? a. alendronate b. calcitriol c. cinacalcet d. sevelamer

Answer 75

a. alendronate: bisphosphonate, treats osteoporosis b. calcitriol: active form of Vit. D, treats hypocalcemia (better than calcidiol, which requires parathyroid hormone for conversion) c. cinacalcet: calcimimetic, activates calcium-sensing receptors in PTH gland (decreases PTH release) d. sevelamer: phosphate-binding polymer (decreases absorption in GI tract), treats hyperphosphatemia in dialysis patients

Question 76

17 YO girl has fatal aortic dissection. Autopsy shows a small and under developed uterus. Ovaries are primarily composed of connective tissue. Which of the following additional abnormalities is most likely to be found in this patient? a. lens displacement. b. Mitral valve prolapse. c. Nephroblastoma. d. Pituitary adenoma e. Renal fusion.

Answer 76

e. Renal fusion - aka horseshoe kidneys dx: **Turner syndrome (45, X)**: most common cause of ovarian dysgenesis, ovarian follicles replaced by connective tissue (streak ovaries) Extragonadal manifestations: short stature, broad chest, webbed neck, bicuspid aortic valve and aortic coarctation (risk for aortic dissection), horseshoe kidney (may cause UTIs)

Question 77

what cardiac syndromes do the following physical examination findings represent? a. beat to beat variation in pulse amplitude b. Drop in pulse amplitude during inspiration. c. Pulse with two distinct peaks. d. Rapidly riding pulse with high amplitude. e. Slow rising, low amplitude pulse.

Answer 77

a. beat to beat variation in pulse amplitude (*pulsus alternans*) = severe LV systolic dysfunction b. Drop in pulse amplitude during inspiration (*pulsus paradoxus*) = cardiac tamponade c. Pulse with two distinct peaks (*dicrotic pulse*) = severe systolic dysfunction + high SVR d. Rapidly riding pulse with high amplitude (*hyperkinetic pulse*) = aortic regurgitation or high-output heart failure (rapid ejection of large stroke volume against decreased afterload) e. Slow rising, low amplitude pulse (*pulsus parvus et tardus*) = fixed LV outflow obstruction (aortic stenosis), due to diminished SV + prolonged LV ejection time

Question 78

name the nerve that innervates the following (be specific): a. General sensation in the anterior tongue b. sensation in lower lip. c. Taste sensation in anterior tongue d. Masseter muscle.

Answer 78

a. General sensation in the anterior tongue = lingual nerve (branch of CN V3) b. sensation in lower lip = inferior alveolar nerve (branch of CN V3) c. Taste sensation in anterior tongue = chorda tympani nerve (branch of CN VII) d. Masseter muscle = anterior division of CN V3

Question 79

describe two mechanisms by which hyperphosphatemia in chronic kidney disease (CKD) induces hypocalcemia

Answer 79

1. Phosphate find two free calcium and precipitates in soft tissues —> vascular calcification 2. Increased serum phosphate triggers release of fibroblast growth factor 23 from bone, which acts to lower phosphate levels in part by inhibiting renal expression of 1-alpha hydroxylase. This reduces production of 1,25-dihydroxy vitamin D (calcitriol), leading to reduce intestinal calcium absorption

Question 80

thick walled spherules, larger than RBCs, packed with endospores =

Answer 80

*coccidioides immitis*: dimorphic fungus, that is endemic to the desert areas of the United States and Mexico Causes lung disease in immunocompetent patients and disseminated disease in immunocompromised patients

Question 81

what would lab values show in a patient with lamellar bone structure resembling a mosaic pattern?

Answer 81

NOTHING - serum calcium and phosphorus in Paget disease of bone are NORMAL

Question 82

22yo unvaccinated woman comes to office due to a rash that developed during recent trips to southeast Asia. While abroad she developed a low-grade fever and arthralgias, followed by numerous pinpoint, pink macules and papules on her face. These spread to the trunk and then extremities. The woman is pregnant. What infectious illness did she have, and what complications is the fetus at risk for?

Answer 82

**rubella**: maculopapular rash with cephalocaudal spread + polyarthritis/arthralgia + postauricular lymphadenopathy fetal complications include *sensorineural hearing loss, cataracts, patent ductus arteriosus, growth restriction, microcephaly*

Question 83

hydrocephalus + chorioretinitis = congenital ______

Answer 83

hydrocephalus + chorioretinitis = congenital *toxoplasmosis* (*Toxoplasma gondii*)

Question 84

meningitis + malformed teeth = congenital ______

Answer 84

meningitis + malformed teeth = congenital *syphilis*

Question 85

Mucocutaneous vesicles + keratitis = congenital _____

Answer 85

Mucocutaneous vesicles + keratitis = congenital *herpes simplex virus (HSV)*

Question 86

what is the cause and presentation of alkaptonuria?

Answer 86

**alkaptonuria**: AR deficiency of homogentisic acid dioxygenase (metabolizes homogentisic acid into maleylacetoacetate) - involved in tyrosine metabolism —> severe arthritis in adult life, accumulation of homogentisic acid in connective tissue causing pigment deposits (blue-black deposits in sclerae) + ankylosis (spine) urine turns black when exposed to air due to oxidation of homogentisic acid

Question 87

urine turns black when exposed to air =

Answer 87

**alkaptonuria**: AR deficiency of homogentisic acid dioxygenase (metabolizes homogentisic acid into maleylacetoacetate) - involved in tyrosine metabolism —> severe arthritis in adult life, accumulation of homogentisic acid in connective tissue causing pigment deposits (blue-black deposits in sclerae) + ankylosis (spine) urine turns black when exposed to air due to oxidation of homogentisic acid

Question 88

adult with severe arthritis + blue-black spots on sclerae =

Answer 88

**alkaptonuria**: AR deficiency of homogentisic acid dioxygenase (metabolizes homogentisic acid into maleylacetoacetate) - involved in tyrosine metabolism —> severe arthritis in adult life, accumulation of homogentisic acid in connective tissue causing pigment deposits (blue-black deposits in sclerae) + ankylosis (spine) urine turns black when exposed to air due to oxidation of homogentisic acid

Question 89

what are the clinical findings of the following neonatal umbilical disorders? a. umbilical granuloma b. patent urachus c. patent omphalomesenteric duct d. omphalitis

Answer 89

a. umbilical granuloma: serous umbilical moisture, pedunculated mass b. patent urachus: urine leakage c. patent omphalomesenteric duct: stool leakage (bowel connected to umbilicus) d. omphalitis: purulent drainage, induration/erythema

Question 90

what cardiac defect can be caused by implantation of a permanent pacemaker?

Answer 90

*tricuspid valve regurgitation* - right ventricular lead of pacemaker passes though tricuspid valve orifice and can disrupt valve closure

Question 91

what does neuroimaging of Huntington’s show?

Answer 91

enlargement of frontal horns of lateral ventricles - due to atrophy of caudate nuclei

Question 92

6mo is in 10th percentile of growth and exam shows hepatomegaly and hypotonia. Labs show hypoglycemia and ketoacidosis. Liver biopsy shows hepatic fibrosis without fat accumulation. There is accumulation of abnormally structured polysaccharides within the cytosol of the hepatocytes. What enzyme is deficient?

Answer 92

**glycogen debranching enzyme** —> deficiency (*Cori disease*) affects both liver and muscle, abnormal glycogen accumulates in glycogenolysis, *glycogen phosphorylase* cleaves glycogen linkages, leaving glucose-1-phosphate… when 4 residues remain, **debranching enzyme** moves the first 3 residues to a nearby branch and *alpha-1,6-glucosidase* removes the last residue

Question 93

which glycogen storage disease causes accumulation of *normally* structured glycogen on liver biopsy?

Answer 93

*Hers disease* = deficiency of **liver glycogen phosphorylase** —> mild hypoglycemia, ketosis, hepatomegaly, excess of normally structured glycogen on liver biopsy (does NOT affect muscle)

Question 94

32yo M presents with low-grade fever and malaise. Surgical history include tonsillectomy and tympanostomy tube replacement at 8yo. Pt just returned from trip to Great Lakes. KOH prep shows large yeast cell with single bud. When incubated at 24C, a multicellular structure with branching, tubular cells grow. What is the dx?

Answer 94

**Blastomyces dermatitis** - localized to Ohio and Mississippi River valleys + Great Lakes region, found in soil lab shows doubly refractile wall and single broad-based bud

Question 95

name 5 dimorphic fungi

Answer 95

form molds (w/ hyphae) in 25-30C and yeasts (single cells) in 37C (body temp) 1. sporothrix schenckii 2. coccidioides immitis 3. histoplasma capsulatum 4. blastomyces dermatitis 5. paracoccidioides brasiliensis

Question 96

what happens to the segment of proinsulin that is removed during post-translational processing?

Answer 96

proinsulin is transported to Golgi apparatus and packed into secretory granules **C-peptide** is cleaved from proinsulin (via endopeptidases) and *stored in secretory granules*, then secreted via exocytosis

Question 97

posterior hip dislocation is most likely to damage: a. femoral artery b. femoral nerve c. lateral femoral cutaneous nerve d. sciatic nerve e. superior gluteal artery

Answer 97

d. sciatic nerve - runs posterior to the hip joint, damage will present as weak ankle dorsiflexion + decreased sensation (common peroneal + tibial) a. femoral artery/ b. femoral nerve - injured in anterior dislocation c. lateral femoral cutaneous nerve - risk of external compression (under inguinal ligament) e. superior gluteal artery - injured in pelvic fracture

Question 98

when a patient presents with chest pain and ST elevation, when should you be thinking about vasospastic angina?

Answer 98

*young patient* (<50) with *minimal CAD risk factors* (other than smoking - big risk factor due to endothelial dysfunction) + *recurrent chest discomfort at rest or during sleep* (when vagal tone is at peak) that *spontaneously resolves* <15 mins

Question 99

what is the mechanism by which opioids cause itching and wheezing?

Answer 99

opioids generate pseudo-allergic response via *direct mast cell degranulation* (non-IgE mediated)

Question 100

64yo M presents with LLE pain/swelling/redness over past 3 days with fever. PMH sig. for HTN and obesity. PE shows diffuse erythema extending up midcalf with indistinct border. There is warmth and edema. Lab shows neutrophilic leukocytosis and Doppler is neg. for DVT. What is the dx (be specific)?

Answer 100

**cellulitis** if nonpurulent (no fluctuant nodules), most likely *beta-hemolytic streptococci* (usually Strep. pyogenes, Group A) if purulent, most likely *Staph. aureus*

Question 101

which of the following drugs is most likely to cause anticholinergic toxicity? a. amitriptyline b. diazepam c. haloperidol d. prazosin e. propranolol f. sertraline

Answer 101

a. **amitriptyline** = TCA b. diazepam = benzodiazepine c. haloperidol = first gen. antipsychotic d. prazosin = alpha1 blocker e. propranolol = non-selective beta blocker f. sertraline = SSRI