UWorld Test Reviews Flashcards
(100 cards)
1
Q
most African Plasmodium species are _______ resistant and require treatment with ________ or __________
A
most African Plasmodium species are chloroquine resistant and require treatment with atovaquone-proguanil or artemisinins
2
Q
where is ventilation and perfusion highest/lowest in the lungs?
A
ventilation and perfusion are both lowest in the apex and highest in the base - gravity pulls lungs downward, expanding alveoli and increasing blood flow at the base
however, gravitational effect on perfusion is greater than ventilation —> V/Q ratio is LOWEST at the BASE and highest at the apex
3
Q
large pulmonary arteriovenous malformations (AVMs) may cause:
a. alveolar diffusion impairment
b. decreased alveolar ventilation
c. increased pulmonary vascular resistance
d. increased R to L shunting
A
AVM allows direct artery to vein anastomosis —>
d. increased R to L shunting
deoxygenated blood is directly arterialized without participating in gas exchange —> hypoxemia
4
Q
what is the function of O6-methylguanine-DNA methyltransferase (MGMT)?
A
converts O6-methylguanine (naturally occurring alkylation product) back to guanine
5
Q
what are the clinical features of 22q11.2 deletion?
A
aka DiGeorge Syndrome, CATCH-22:
Cardiac outflow tract anomalies (tetralogy of Fallot, truncus arteriosus)
Anomalous face (prominent nasal bridge, low-set ears, micrognathia)
Thymic aplasia (decreased T cell immunity)
Cleft palate
Hypoparathyroidism (hypoCa2+)
6
Q
which of the following as a structure most closely resembling endorphins?
a. prolactin
b. TSH
c. ACTH
d. growth hormone
e. vasopressin
f. somatomedin C (insulin like growth factor)
A
c. ACTH
endorphins, ACTH, and MSH are all derived from POMC (proopiomelanocortin) - suggests physiological relationship between stress axis and opioid system
7
Q
what can be used to distinguish cardiogenic vs no cardiogenic pulmonary edema?
A
noncardiogenic pulmonary edema (ARDS, high altitude pulmonary edema) has a normal pulmonary capillary wedge pressure
[clinical history of pneumonia/sepsis or pancreatitis is also suggestive of ARDS]
cardiogenic pulmonary edema (decompensated LVHF, volume overload) will have elevated PCWP
8
Q
where would lipofuscin granules be found, and in which patients?
A
lipofuscin: insoluble granules composed of lysosomal breakdown products (lipid polymers, phospholipids) resulting from free radical injury and lipid peroxidation
wear-and-tear products that accumulate with age in low-turnover cells (heart, liver, CNS) of elderly
9
Q
what is the mechanism for glucose entry into cells?
A
carrier-mediated (facilitated) transporter - does NOT require ATP
10
Q
heparin induced thrombocytopenia type 2
A
formation of IgG Abs to complexes of heparin + endogenous platelet factor 4
—> thrombocytopenia, typically 5-10 days after heparin initiation due to destruction of antibody-coated platelets by splenic macrophages
11
Q
what is the effect of angiotensin II on GFR?
A
angiotensin II preferentially constricts efferent arteriole —> increased hydrostatic pressure, increased net filtration pressure
12
Q
which 2 proximal carpal bones articulate with the radius?
A
scaphoid (lateral) and lunate (medial)
scaphoid more often affected by FOOSH
13
Q
characterized by epithelial and myoepithelial cells lining fibrovascular cores in cyst walls or ducts in the breast
A
intraductal papilloma - most common cause of bloody nipple discharge, typically presents without breast masses or skin changes
14
Q
gingival hyperplasia is a common side effect of:
a. lithium
b. prednisone
c. cocaine
d. phenytoin
e. clozapine
f. methimazole
A
d. phenytoin - causes increased expression of PDGF, which causes proliferation of gingival tissue and alveolar bone
phenytoin toxicity mainly affects cerebellum and vestibular system —> ataxia, nystagmus
15
Q
which 2 bacteria cause a purely toxin-mediated watery diarrhea?
A
- Vibrio cholerae
- enterotoxigenic Escherichia coli
modify electrolyte handling by enterocytes but do not cause cell death - no erythrocytes or leukocytes are noted in stool microscopy
16
Q
patients with deficiency of propionyl-CoA carboxylase are unable to utilize which amino acids for energy production?
A
propionyl-CoA carboxylase required for conversion of propionyl-CoA to methylmalonyl-CoA
propionyl-CoA is derived from metabolism of valine, isoleucine, methionine, threonine, and odd-chain fatty acids
deficiency —> proprionic acidemia, presenting with lethargy, poor feeding, vomiting, hypotonia 1-2 weeks after birth
17
Q
contrast the effect of CFTR functioning in sweat ducts vs respiratory/intestinal glands
A
sweat ducts - reabsorb luminal Cl-, stimulate ENaC Na+ absorption from lumen [mutation —> sweat with high Cl- and Na+ content]
resp/intestinal glands - secrete Cl- ions, inhibit ENaC opening to decrease Na+ reabsorption —> retains water in lumen to form hydrated mucus
18
Q
in preparation for labor, increasing estrogen stimulates production of:
a. adherens junctions
b. desmosomes
c. fenestrae
d. gap junctions
e. hemidesmosomes
f. tight junctions
A
d. gap junctions - via upregulation of connexin proteins
increase in gap junction density allows for coordinated labor contractions
19
Q
what is the effect of nitrites on respiration?
A
nitrites - cause poisoning by inducing conversion of heme iron (Fe2+, ferrous) to oxidized iron (Fe3+, ferric) —> methemoglobin, unable to bind O2
affinity of residual ferrous iron is increased, causing left shift as well
look out for “dusky” discoloration of skin and state of functional anemia
20
Q
what is the function of interferon alpha/beta vs gamma
A
IFN alpha/beta (Type I) —> halt protein synthesis and promote apoptosis of infected cells, induce MHC I expression, stimulate NK and cytotoxic T cells
IFN gamma (Type II) —> produced by NK and T cells, promotes TH1 differentiation, induces MHC II expression on APC, enhances macrophage function
21
Q
coronary dominance is determined by…
A
… which coronary artery supplies blood to the posterior descending artery (PDA)
right dominant (most people) = right coronary artery
left dominant = left circumflex artery
22
Q
what type of host immune factors are responsible for mediating the response to monoclonal antibody therapy?
A
NK cells and granzymes, mediating antibody-dependent cellular cytotoxicity (ADCC)
IgG (natural or mAb) binds surface antigen —> NK binds Fc portion using CD16 —> triggered granule release (perforin + granzymes/proteases) —> induced apoptosis/osmotic lysis
23
Q
which virus infects B cells and stimulates them to proliferate continuously (transformation, aka immortalization)?
A
Epstein-Barr virus (EBV) - EBV-encoded oncogenes activate proliferative and anti-apoptotic signaling in infected B cell
immortalized B cells secrete heterophile IgM antibodies
24
Q
what would muscle biopsy of focal dystonia show?
A
focal dystonia: neurological movement disorder characterized by sustained, involuntary muscle contractions
would cause muscle fiber hypertrophy
25
5 day old with multiple episodes of emesis, tachycardia, hypotension, sunken fontanelle, dry mucous membranes, hepatomegaly, gram negative rods in arterial blood
symptoms started after breastfeeding - which enzyme is impaired?
*galactose-1-phosphate uridyl transferase (GALT)*: converts galactose-1-phosphate to glucose-1-phosphate
patients predisposed to E. coli sepsis
26
what are normal aortic and LV pressures, respectively?
aortic: 120/80
LV: 120/10
27
what types of medications are associated with drug-induced neutropenia? (5)
*antithyroid*: methimazole, propylthiouracil
anti-inflammatory: sulfasalazine, methotrexate
psychotic/anticonvulsant: clozapine, carbamezepine, phenytoin
cardio: anti-arrhythmic (procainamide), ticlopidine
antimicrobial: TMP-SMX, quinine, acyclovir
28
how does drug-induced neutropenia present?
oropharyngeal ulcers + fever (mucus membrane infection)
lab shows isolated leukopenia (no anemia, thrombocytopenia)
resolves in 1-3 weeks if drug is discontinued
29
which infectious disease is associated with thatched roofing/ adobe in Latin America?
*Trypanosoma cruzi*: vector-borne to Triatomine bug, causes *Chagas disease*
acute phase: asymptomatic or nonspecific
chronic phase: 1-3 decades later, minority develop end-organ disease of heart (cardiomyopathy - ventricular arrhythmias!) or GI system
30
when are beta-hCG levels first detectable in serum after fertilization?
8 days after fertilization
31
malignant breast condition characterized by unilateral, painful/pruritic, eczematous rash confined to nipple and areola, associated with scaling/ulceration
Paget disease of the breast (adenocarcinoma) - biopsy shows Paget cells in epidermis of nipple-areolar complex (enlarged, abundant cytoplasm, prominent nucleoli)
most patients have underlying breast malignancy - require diagnostic mammography
32
forms colonies in culture with multiple curled extensions at the edges that resemble a “Medusa head”
bacillus anthracis: large, nonmotile, nonhemolytic, gram positive rod
33
facial muscle contractions elicited by tapping on the facial nerve anterior to the ear is indicative of what
hypocalcemia - causes neuromuscular hyperexcitability
becomes clinically apparent when serum calcium drops below 7mg/dL
34
from where do the gonadal arteries vs gonadal veins arise from?
gonadal arteries arise from *abdominal aorta* (involved in testicular torsion)
R gonadal vein drains into IVC, L gonadal vein drains into *left renal vein* (affected by blockage by tumor)
35
Pt is 24yo F presenting with pruritic rash on her flexor regions (antecubital and popliteal fossa), which has been present on and off for most her life. Examination reveals erythematous patches and papules. What is the diagnosis, and which cytokines are driving the pathology?
*atopic dermatitis*: inflammatory condition characterized by acute exacerbations of dry, pruritic, erythematous patches, papules, or vesicles in flexural regions
pathology - skin barrier dysfunction increases cutaneous exposure to environmental antigens, which induces Th2 response, triggered by *IL-4 and IL-13* —> IgE production, inhibition of Th1
36
by what mechanism does amiodarone affect digoxin metabolism?
inhibition of *P-glycoprotein* (transmembrane efflux transporter, aka drug pump) —> increased intestinal absorption + decreased renal clearance
[note amiodarone does inhibit cytochrome P-450, but digoxin is NOT hepatically cleared and therefore unaffected by this]
37
gingival bleeding + failed ristocetin test + corrected ristocetin test with normal plasma added =
*Von Willebrand factor deficiency*
vWF binds glycoprotein Ib receptors on platelets following endothelial damage - mediates platelet adherence
ristocetin cofactor assay measures platelet agglutination via binding of glycoprotein Ib receptors to vWF (activates receptors to make them available for binding)
38
what anatomical landmark should be used to identify the optimal site for lumbar puncture?
iliac crest - needle should be inserted in the L3/L4 of L4/L5 space
[recall spinal cord terminates at inferior border of L1 vertebra in adults, L2/L3 in neonates/infants]
39
neutrophil micro-abscesses + epidermal hyperplasia (acanthosis) =
psoriasis: erythematous plaques with thick scales on extensor surfaces of extremities
40
hyperkeratosis + sawtoothed rete ridges =
lichen planus: small, pruritic, purplish, polygonal papules or plaques
typically multi-focal
41
which 2 pathogens may colonize the upper female genital tract and cause tubal scarring, increasing the risk of ectopic pregnancy?
1. Neisseria gonorrhoeae
2. Chlamydia trachomatis
both cause cervicitis, which comprises cervix barrier and allows bacterial ascent
recall tubal scarring is most common risk factor for ectopic pregnancy
42
young child + history of abscesses + inactivating mutation affecting neutrophil oxidation = susceptibility to what type of organisms?
*chronic granulomatous disease*: X-linked recessive mutation in NADPH oxidase —> impaired respiratory burst —> impaired phagocytic intracellular killing
susceptible to *catalase-positive bacteria* (+ aspergillus fungi)
this is because catalase allows these organisms to break down their own H2O2, preventing immune cells from scavenging it for use
43
how does Bacillary angiomatosis present, and what is it caused by?
infection of *Bartonella henselae*: gram neg. bacteria, reservoir is domesticated cats (transmission via scratches)
healthy patients develop regional lymphadenopathy, immunocompromised (*advanced AIDS*) develop *highly vascular cutaneous lesions which bleed profusely* (no pus)
biopsy shows large endothelial cells forming small vascular channels surrounded by inflammatory infiltrate
44
what are the steps of catecholamine synthesis? (4) include enzymes
1. tyrosine —> DOPA via *tyrosine hydroxylase*
2. DOPA —> dopamine via *dopa decarboxylase*
3. dopamine —> NE via *dopamine beta-hydroxylase*
4. NE —> epinephrine via *PNMT (phenylethanolamine-N-methyltransferase)* - also note this enzyme is activated by cortisol
45
how does cortisol up-regulate catecholamine synthesis? be specific
1. tyrosine —> DOPA via tyrosine hydroxylase
2. DOPA —> dopamine via dopa decarboxylase
3. dopamine —> NE via dopamine beta-hydroxylase
4. *NE —> epinephrine* via *PNMT (phenylethanolamine-N-methyltransferase)* - *this enzyme is activated by cortisol*
46
which of the following describes a finding of chronic allograft rejection?
a. dense mononuclear interstitial infiltrate.
b. glomerular crescent formation.
c. Obliterative vascular fibrosis.
d. Tubular hypertrophy and intratubular casts.
e. vascular fibrinoid necrosis with thrombotic occlusion.
*c. Obliterative vascular fibrosis = chronic allograft rejection*
a. dense mononuclear (lymphocytic) interstitial infiltrate = acute allograft rejection
e. vascular fibrinoid necrosis with thrombotic occlusion = hyper-acute rejection (preformed antibodies)
47
age and co-morbidities such as HTN and HF may predispose to atrial fibrillation development because of…
atrial structural remodeling
these risk factors cause atrial dilation
48
age-related conduction system fibrosis is a primary contributor to what kind of pathology?
*bradyarrhythmias* - such as sinus bradycardia (sick sinus syndrome) or atrioventricular block
49
how would CO poising affect the following blood concentrations?
a. carboxyhemoglobin
b. PaO2
c. methemoglobin
CO poisoning would only increase carboxyhemoglobin! Binds hemoglobin with higher affinity than O2 —> decreases O2 carrying capacity and oxygen content, but does NOT affect amount of dissolved O2 (partial pressure, PaO2)!
[methemoglobin is formed when Fe2+ (ferrous) is oxidized to Fe3+ (ferric)]
50
acute monoarthritis + fever + decreased joint mobility warrants immediate evaluation for…
septic arthritis!
if this is ruled out, other causes of acute monoarthritis include gout, hemarthrosis, and rheumatic disease
51
what is the cause of pulmonary alveolar proteinosis (PAP)?
rare condition characterized by progressive respiratory dysfunction caused by *accumulation of surfactant* debris within alveolar spaces
this due to impaired function of *alveolar macrophages*, usually because of defects in *GM-CSF* signaling
biopsy will show lipoproteinaceous material (surfactant) that is periodic acid-Schiff positive, and forms lamellar bodies within alveolar spaces visible on electron microscopy
52
which of the following describes abdominal aortic aneurysm (AAA)?
a. chronic transmural inflammation
b. cystic medial necrosis
c. focal intimal tear
d. vasa vasorum endarteritis
a. *chronic transmural inflammation*
b. cystic medial necrosis = Marfan syndrome
c. focal intimal tear = aortic dissection
d. vasa vasorum endarteritis = syphilis mediated thoracic aortic aneurysm
53
what is the mutation that causes tuberous sclerosis?
AD LOF mutation in *TSC1* or *TSC2* tumor suppressor genes —> defective *tuberin-hamartin complex* (regulate mTOR pathway signaling) —> enhanced mTOR signaling and unrestricted cellular proliferation
presents with ash-leaf skin spots, facial angiofibromas, Shagreen patches, CNS hamartomas, seizures, intellectual disability, rhabdomyomas (cardiac), angiomyolipomas (renal)
54
what are the classic findings of tuberous sclerosis? (sort it out by body system affected!)
[LOF mutation in TSC1/2 —> defective tuberin-hamartin complex —> overactive mTOR]
1. ash-leaf skin spots
2. facial angiofibromas
3. Shagreen patches
4. CNS hamartomas
5. seizures
6. intellectual disability
7. cardiac rhabdomyomas
8. renal angiomyolipomas
55
common in nursing homes, stains poorly with Gram stain but visualized with silver, causes febrile illness with myalgia, dyspnea, and diarrhea
Legionella pneumonia: sputum Gram stain shows many neutrophils but few/no bacteria (stain poorly), typically detected via urine antigen test, can be visualized with silver stain and grown on buffered charcoal yeast extract agar supplemented with L-cysteine and iron (ground-glass colonies)
typically causes multifocal pneumonia preceded by nonspecific symptoms
56
what are the clinical symptoms of systemic lupus erythematosus?
constitutional: fever, fatigue, weight loss
MSK: *symmetric migratory arthritis*
skin: *butterfly rash*, photosensitivity
serositis: pleurisy, *pericarditis*, peritonitis
heme: thromboembolic events (due to vasculitis and anti-phospholipid antibodies)
57
what are the laboratory findings of systemic lupus erythematosus? (4)
1. hemolytic anemia, thrombocytopenia, leukopenia
2. *hypocomplementemia* (C3, C4)
3. *antinuclear antibodies* (sensitive) + *anti-dsDNA* and *anti-Smith* antibodies (specific)
4. proteinuria and elevated creatinine (renal involvement)
58
what type of hypersensitivity is system lupus erythematosus?
both II and III!
type II hypersensitivity: antibody mediated cell destruction - antinuclear Abs, anti-dsDNA Abs, anti-Smith Abs (cause phagocytic destruction, cytopenias)
type III hypersensitivity: immune complex deposition, commonly i affects skin/mucosa/kidneys/synovium
59
bacteria capable of causing life-threatening invasive infections such as pneumonia and meningitis, major virulence factor is polysaccharide capsule with extensive antigenic variation (leading to 90+ serotypes)
*Streptococcus pneumoniae*: Gram + lancet-shaped diplococcus
childhood vaccine is 13-valent pneumococcal capsular polysaccharide-conjugate vaccine (PCV13) - does not provide protection against strains not included in the vaccine
60
uterus is uniformly enlarged and tender + painful/heavy menstrual bleeding =
*adneomyosis*: endometrial glands and stroma within the uterine myometrium
61
anti-cyclic citrullinated peptide antibodies =
rheumatoid arthritis
62
abnormal proline hydroxylation is caused by a deficiency in which vitamin?
*vitamin C (ascorbic acid)*: required for hydroxylation of proline and lysine (collagen synthesis)
deficiency = Scurvy (easy bleeding/bruising, gingivitis, follicular hyperkeratosis)
63
what is the nutritional deficit behind each of the following?
a. abnormal oxidative decarboxylation of ketoacids
b. abnormal proline hydroxylation.
c. Abnormal transamination.
d. Deficient methionine synthesis.
e. Diminished synthesis of purines.
a. oxidative decarboxylation of ketoacids = thiamine (B1)
b. proline hydroxylation = ascorbic acid (C)
c. transamination = pyridoxine (B6)
d. methionine synthesis = Vitamin B12
e. synthesis of purines = folate
64
differentiate how competitive versus noncompetitive inhibitors affect the Michaelis-Menten curve
Competitive inhibitors: bind to active site and compete with the substrate - additional substrate required to reach 1/2 V max, thereby increasing apparent Km, but Vmax is unchanged
Noncompetitive inhibitors: bind at allosteric site, resulting in a confirmational change of the enzyme that decreases enzymatic activity, and slows the rate of reaction/Vmax. Noncompetitive inhibition does not change the apparent Km, and cannot be overcome with higher substrate concentration.
65
What is first-line therapy for cytomegalovirus (CMV) and what side effects should be expected?
patience to undergo organ transplantation and are on immunosuppressive therapy are at risk for CMV reactivation with end-organ disease
tx: *ganciclovir*: guanine nucleoside analogue —> however, also blocks host DNA polymerase to a lesser degree, which can lead to hematologic side effects such as neutropenia, anemia, and thrombocytopenia
66
what is the preferred first line disease modifying treatment for patients with moderate to severe rheumatoid arthritis, what side effects should be expected?
*Methotrexate*: folate antimetabolite that halts purine and pyrimidine synthesis through competitive inhibition of dihydrofolate reductase
Also causes toxicity to tissues with rapid cellular turnover —> ulcerations, alopecia, pancytopenia, hepatotoxicity, pulmonary fibrosis
67
what would be the histological findings of acute allograft rejection?
*dense interstitial lymphocytic infiltrate* (cell-mediated damage)
humoral - will see C4d deposition, neutrophilic infiltrate, necrotizing vasculitis
68
hypotension, point of maximal impulse is not palpable, heart sounds are distant, enlargement of cardiac silhouette =
cardiac tamponade - presents with Beck triad: hypotension + JVD + distant heart sounds
etiology: blood in pericardial space (LV rupture, cardiac surgery) or pericardial effusion (malignancy, infection, uremia)
ECG shows low-voltage QRS complex and electrical alternans
69
match the side effect with the medication for diabetes mellitus:
a. acute pancreatitis
b. renal dysfunction
c. symptomatic hypoglycemia
d. vitamin B12 deficiency
e. vulvovaginal candidiasis
a. acute pancreatitis = GLP-1 agonists (exenatide, liraglutide) - slow gastric emptying
b. renal dysfunction = SGLT2 inhibitors (“-gliflozin”) - osmotic diuresis can exacerbate dehydration
c. symptomatic hypoglycemia = sulfonylureas, meglitinides - cause glucose-independent insulin release
d. vitamin B12 deficiency = metformin - decreases absorption
e. vulvovaginal candidiasis = SGLT2 inhibitors (“-gliflozin”) - increased urinary glucose
70
DiGeorge syndrome (22q11.2 microdeletion) is caused by maldevelopment of which embryological structures?
third (inferior parathyroid and thymus) and fourth (superior parathyroid) pharyngeal pouches
—> parathyroid and thymic hypoplasia —> hypocalcemia, T cell deficiency
71
young woman + PMH of HTN + intracranial hemorrhage + tortuous appearing carotid arteries with alternating areas of fibrotic webs and aneurysmal dilations (bilaterally) on autopsy =
*fibromuscular dysplasia*: loss of internal elastic lamina, luminal stenosis with alternating areas of aneurysmal dilation, most common in young women (<55)
will present with resistant HTN, renal artery stenosis, CNS involvement (vascular)
“string of beads” appearance on angiography
72
cause/presentation of hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber syndrome)
AD mutation in TGF-beta signaling —> disputed angiogenesis and loss of vascular integrity —> arteriovenous malformations (AVMs)
—> mucocutaneous telangiectasia, recurrent epistaxis, GI bleeding, hemoptysis, hemorrhagic stroke
—> high output heart failure, pulmonary HTN (cyanosis, clubbing, dyspnea when upright), paradoxic embolism, iron deficiency anemia
73
cause and presentation of cysticercosis
ingestion of *Taenia solium* (pork tapeworm) eggs (fecal-oral) - higher risk in developing nations
—> adult-onset seizures (3-5 years after transmission), subcutaneous nodules, cigar-shaped muscle lesions
brain imaging shows round, viable cysts or calcified nodules
74
which of the following is most closely associated with holoprosencephaly?
a. Congenital rubella syndrome.
b. Intrauterine Zika virus infection
c. Maternal lithium use.
d. Trisomy 13.
d. Trisomy 13
also associated with sonic hedgehog gene mutations and maternal alcohol or retinoic acid use
congenital rubella = triad of sensorineural hearing loss + Cataracts + Congenital heart disease (PDA)
Zika infection = microcephaly, intracranial calcifications, ventriculomegaly
Maternal lithium = cardiac abnormalities (Ebstein anomaly)
75
which of the following would most likely be observed in a patient with a PICA stroke?
a. left-sided motor weakness, including lower facial region.
b. Lots of conjugate lateral gaze on both sides.
c. Sensory loss over the right side of the face and left side of the body.
c. Sensory loss over the right side of the face and left side of the body.
lateral medullary (Wallenberg) syndrome —> damage to vestibular nuclei (vertigo, nystagmus), inferior cerebellar peduncle (ataxia), spinal trigeminal nucleus (loss of pain/temp to ipsilateral face), spinothalamic tract (loss of pain/temp to contralateral body), nucleus ambiguus (bulbar weakness - dysphagia)
76
which of the following confers the greatest risk for *Clostridium septicum* infection?
a. colonic malignancy
b. Hemochromatosis.
c. Indwelling vascular catheter.
d. Multiple myeloma.
e. Recent antibiotic use.
a. colonic malignancy
Clostridium septicum: spore-forming, exotoxin producing, gram-positive bacteria that is normal commensal of the G.I. tract in humans
Largely non-pathogenic, but breakdowns in G.I. mucosa can lead to invasion with subsequent hematogenous dissemination to healthy muscle tissue, resulting in spontaneous gas gangrene
Most cases of spontaneous gas gangrene are triggered by an underlying colonic malignancy, which creates a portal of entry for bacteria
77
which drug classes improve mortality in patients with chronic heart failure with reduced ejection fraction? (6) name one drug from each class
1. angiotensin receptor-neprilysin inhibitors; sacubitril-valsartan
2. ACE inhibitors; lisinopril
3. ARBs; losartan
4. beta blockers; metoprolol, carvedilol
5. mineralocorticoid receptor antagonists; spironolactone, eplerenone
6. SGLT2 inhibitors; dapagliflozin, empagliflozin
78
Which calcium channel blockers are specifically contraindicated in heart failure with reduced ejection fraction due to the potential for reduced contractility and further worsening of LV systolic dysfunction?
nondihydropyridine Ca2+ channel blockers: *verapamil, diltiazem*
79
Within the true pelvis, a surgeon can most likely palpate the right ureter immediately anterior to which structure?
a. Gonadal vein.
b. Inferior vena cava.
c. Internal iliac artery.
d. Round ligament.
e. Uterine artery.
c. Internal iliac artery.
80
what is the most effective preventative innervation in almost all patients (for those who it applies) in decreasing mortality risk?
smoking cessation
81
define the following types of congenital anomalies:
a. deformation
b. disruption
c. dysplasia
d. malformation
a. deformation: mechanical forces alter shape/position of a structure that was previously developing normally
b. disruption: destruction of a structure that was previously developing normally
c. dysplasia: abnormal organization of cells within a tissue (often genetic)
d. malformation: defect in organogenesis (genetic, teratogenic)
82
what is the probability that a sibling will be an identical HLA match?
1/4
HLA genes are encoded on MHC molecules in clusters - low rate of crossover - therefore, offspring essentially inherit 2 HLA haplotypes, one from each parent
83
what transport proteins mediate retrograde vs anterograde axonal transport?
retrograde = *dynein*
anterograde = *kinesin*
84
CTG trinucleotide repeat - what disease is this and how does it present?
*myotonic dystrophy type 1*: AD muscular dystrophy, CTG repeats cause mutant mRNAs that are not translated and accumulate
affects non-dividing cells the most - skeletal muscle, brain, myocardium
85
nephritic syndrome in a child preceded by an erythematous, macular rash over legs/back =
*IgA vasculitis (Henoch-Schonlein purpura)*: deposition of IgA following URI, complement activation, neutrophilic inflammation
presents with palpable purpura/petechiae on lower extremities, arthritis/arthralgia, abdominal pain or GI bleeding, IgA deposition in mesangium
86
Patient with history of chronic alcohol use disorder and malnourishment comes to ED and is given thiamine, folic acid, multivitamin, and dextrose-containing IV fluids. A few hours later, the patient develops marked muscle weakness and serum phosphate levels are low. Explain.
*refeeding syndrome*: occurs after reintroduction of carbohydrates in patients with chronic malnourishment - stimulates insulin secretion and drives phosphorus intracellularly for ATP production
redistribution into hepatic and muscle cells causes severe hypophosphatemia
87
2 year old child with urine that turns black if let sit (oxidize) =
*alkaptonuria*: AR disorder of *tyrosine metabolism*
can’t convert tyrosine to fumarate, causing *homogentisic acid* to accumulate and be excreted in urine - turns black if allowed to oxidize
retained homogentisic acid selectively binds collagen and can cause “ochronosis”: blue-black pigmentation in ears/nose/cheeks
88
what is the cause and presentation of alkaptonuria?
*alkaptonuria*: AR disorder of *tyrosine metabolism*
can’t convert tyrosine to fumarate, causing *homogentisic acid* to accumulate and be excreted in urine - turns black if allowed to oxidize
retained homogentisic acid selectively binds collagen and can cause “ochronosis”: blue-black pigmentation in ears/nose/cheeks
89
what occurs from impaired metabolism of branched-chain amino acids such as leucine, isoleucine, and valine?
*maple syrup urine disease*: branched-chain amino acids cannot be converted to acetoacetate
—> cerebral edema, seizures, sweet smelling urine
90
in patients with an inability to convert phenylalanine to tyrosine, which enzyme is deficient, and what is the clinical consequence?
aka *phenylketonuria (PKU)*: defect in phenylalanine hydroxylase, phenylalanine can’t be converted to tyrosine
—> significant intellectual disability (if not treated)
91
patient can’t convert serine to cysteine - how will this present?
aka *cystinuria*: flank pain + hematuria + renal stones in childhood or adolescence
92
chest x-ray shows round density with an air-fluid level, patient has fever and cough with copious sputum… what does this indicate?
*lung abscess*: necrotic infection of pulmonary parenchyma
most cases due to aspiration of anaerobic bacteria, can also occur in setting of untreated pneumonia
formation of lung abscess driven by *neutrophils* releasing cytotoxic granules (lysosomal content) containing myeloperoxidase and other digestive enzymes
93
what type of immune cell drives the formation of lung abscess?
*lung abscess*: necrotic infection of pulmonary parenchyma, most cases due to aspiration of anaerobic bacteria
formation of lung abscess driven by *neutrophils* releasing cytotoxic granules (lysosomal content) containing myeloperoxidase and other digestive enzymes
94
which virus is dependent on CD21 for cellular entry?
*Epstein-Barr virus* - EBV envelope glycoprotein gp350 binds CD21 (aka CR2), which is the cellular receptor for the *C3d complement component*
CD21 normally present on surface of B cells
95
Pityriasis versicolor (tinea versicolor) is a superficial skin infection which causes erythematous, hyper- or hypo-pigmented macules or patches. It is caused by _______
*Malassezia globosa*: forms spores and hyphae in characteristic “spaghetti and meatballs” appearance on KOH preparation light microscopy
infection confined to stratum corneum, common in hot/humid climates, most visible after extensive sun exposure due to tanning of adjacent skin
most cases occur in healthy individuals
96
how does infection by *Malassezia globosa* present, and in whom?
*Malassezia globosa*: cutaneous fungi, causes *pityriasis versicolor (tinea versicolor)* —> hypo or hyper pigmented erythematous macules or patches on upper body
infection confined to stratum corneum, common in hot/humid climates, most visible after extensive sun exposure due to tanning of adjacent skin
most cases occur in healthy individuals
97
healthy individual in hot/humid environment presenting with hyper or hypo pigmented macules or patches on upper body after prolonged sun exposure = infection with what pathogen?
*Malassezia globosa*: cutaneous fungi, causes *pityriasis versicolor (tinea versicolor)* —> hypo or hyper pigmented erythematous macules or patches on upper body
infection confined to stratum corneum, common in hot/humid climates, most visible after extensive sun exposure due to tanning of adjacent skin
most cases occur in healthy individuals
98
initiation of allopurinol would most likely increase the activity of which of the following medications?
a. azathioprine
b. ganciclovir
c. mycophenolate mofetil
d. tacrolimus
e. trimethoprim
a. azathioprine
allopurinol inhibits xanthine oxidase, which usually converts 10% of purine bases into uric acid for excretion (other 90% are salvaged via HGPRT)
*azathioprine* is metabolized via purine degradation pathway - converted to *6-mercaptopurine (6-MP)*, which is shunted towards HGPRT when xanthine oxidase is inhibited… this causes *accumulation of active metabolites* which incorporate into DNA/RNA and inhibit hematopoietic cell proliferation
99
which of the following best describes the dysfunctional transmembrane protein causing cystic fibrosis?
a. cyclic nucleotide-gated
b. ATP-gated
c. mechanically gated
d. voltage-gated
b. ATP-gated
CF transmembrane conductance regulator (CFTR) opens after binding 2 ATP, allowing transport of chloride ions down electrochemical gradient (and OUT of cell)
movement of Cl- establishes membrane potential that draws sodium and water across membrane as well to hydrate mucosal surfaces
100
which of the following is the best initial treatment for gouty arthritis?
a. cyclooxygenase inhibitor
b. lipoxygenase inhibitor
c. TNF-alpha inhibitor
d. uricosuric agent
e. xanthine oxidase inhibitor
a. cyclooxygenase (COX) inhibitor
NSAIDs are first-line for *acute* treatment - inhibit COX enzymes, decreasing prostaglandin synthesis
[note these are avoided in patients with renal and hepatic disease, alternatives include colchicine and glucocorticoids]
uricosuric agents (probenecid) or xanthine oxidase inhibitors (allopurinol, febuxostat) are for *prevention*
