High yield review 4 Flashcards

Question

DNA defects summary

Answer 1

XP = NER (thymine dimers) Lynch = MMR BRCA1/2 = HR ATM (A-T) = DS break repair (NHEJ) Fanconi = Crosslink repair (NHEJ/HR overlap)

Answer 2

Think of these when patients fail to respond to normal hormone or cytokine levels despite normal receptor expression Glucocorticoid Receptor Polymorphism May alter HPA axis feedback sensitivity 🧠 Tip: Know it as a theoretical basis for steroid resistance or sensitivity variability. Vitamin D Receptor (VDR) Polymorphism: 🧠 Tip: Patient with low bone mineral density despite normal vitamin D and calcium levels. Beta-Adrenergic Receptor Polymorphisms: Asthma patient with poor response to β-agonists → suspect β2 receptor polymorphism Leptin Receptor Mutation: Tip: Obese child with high leptin levels → leptin receptor resistance (vs. leptin deficiency, where leptin is low) Insulin Receptor Mutation: 🧠 Tip: Young woman with acanthosis nigricans + hyperglycemia + high insulin → think receptor-level insulin resistance Androgen Insensitivity Syndrome (AIS): 🧠 USMLE Tip: Female external genitalia + undescended testes + no uterus = complete AIS Serum testosterone = high/normal male range

Answer 3

USMLE Tip: Squamous → columnar = metaplasia from acid exposure 🧠 USMLE Tip: Barrett = precancerous, not yet malignant Adenocarcinoma, not squamous cell (that’s upper esophagus 🧠 USMLE Tip: "Goblet cells in lower esophagus" = hallmark of Barrett metaplasia

Answer 4

Respiratory Alkalosis (↑ pH, ↓ CO₂): 🧠 Tip: Sudden drop in CO₂ → think excessive ventilation or anxiety ARDS Ventilation Strategy Use low tidal volume (6 mL/kg) Use higher PEEP Goal: Prevent volutrauma and atelectrauma 🧠 Tip: ARDS patient → low VT, high PEEP, low plateau pressure 🧠 Tip: If plateau normal, think bronchial issue, not compliance

Answer 5

High Peak and High Plateau Pressure Suggests ↓ lung compliance (e.g., ARDS, pulmonary edema, pneumothorax) 🧠 Tip: If both pressures ↑, the lung is stiff — think parenchymal issue Auto-PEEP (Intrinsic PEEP): Tip: COPD patient + hypotension + high pressure = auto-PEEP Permissive Hypercapnia 🧠 Tip: Prioritize lung protection over perfect CO₂ levels in ARDS

Answer 6

Beat-to-beat variation in pulse amplitude (strong-weak-strong-weak) Indicates left ventricular systolic dysfunction 🧠 USMLE Tip: Seen in advanced heart failure Associated with low stroke volume; may hear S3 gallop

Answer 7

Slow, low-rising upstroke with a notch (delayed systolic peak) Classic in severe aortic stenosis 🧠 USMLE Tip: "Pulsus parvus et tardus" = weak and delayed carotid pulse = aortic stenosis

Answer 8

Normal beat followed by a premature beat (usually a PVC) → weaker pulse Alternating strong and weak beats due to arrhythmia, not stroke volume 🧠 USMLE Tip: Often seen with digoxin toxicity or PVCs Not to be confused with pulsus alternans (which is due to contractility variation)

Answer 9

Two systolic peaks per cardiac cycle Best felt in carotid artery 🧠 USMLE Tip: Classic in: Aortic regurgitation Hypertrophic obstructive cardiomyopathy (HOCM) Combined aortic regurgitation + stenosis

Answer 10

Drop in systolic BP >10 mmHg during inspiration Caused by impaired cardiac filling 🧠 USMLE Tip: Seen in: Cardiac tamponade (most classic) Constrictive pericarditis Severe asthma or COPD Patient with hypotension + distant heart sounds + JVD + pulsus paradoxus = tamponade

Answer 11

. Acute Myocardial Infarction (MI) #1 cause in USMLE scenarios Diaphoresis + chest pain + radiation to jaw/arm ↑ CK-MB, troponin, ECG changes 🧠 Tip: CK-MB used to detect reinfarction; troponin stays elevated longer 🧠 Tip: Young person with viral illness → suspect myocarditis 🧠 Tip: Total CK (not MB isoform) is more elevated in rhabdomyolysis 🧠 Tip: Post-op or shock patient + elevated CK-MB without ischemic symptoms

Answer 12

Metric Effect of ↑ Prevalence Effect of ↓ Prevalence Sensitivity No change No change Specificity No change No change PPV Increases Decreases NPV Decreases Increases 🧠 USMLE Tip: Sensitivity & specificity are fixed for a test, but PPV & NPV vary with prevalence

Answer 13

Definition Normal: <120/<80 mmHg Elevated: 120–129/<80 Stage 1 HTN: 130–139/80–89 Stage 2 HTN: ≥140/≥90 🧠 USMLE Tip: Young woman + HTN + abdominal bruit → think fibromuscular dysplasia Older man + HTN + low K⁺ → think primary hyperaldosteronism 🧠 USMLE Tip: Always investigate secondary HTN in young patients or treatment-resistant cases Don’t use ACE inhibitors in pregnancy (→ fetal renal damage) β-blockers are contraindicated in severe asthma or bradycardia HTN + vision changes, confusion, chest pain = emergency → IV meds needed Hypertensive Emergency vs. Urgency Urgency: ≥180/≥120 without end-organ damage Emergency: ≥180/≥120 with end-organ damage (e.g. encephalopathy, MI, stroke, papilledema) 🧠 USMLE Tip: HTN + vision changes, confusion, chest pain = emergency → IV meds needed

Answer 14

Comorbidity First-line Drug(s) No comorbidity Thiazide, ACEi, ARB, CCB Diabetes ACEi or ARB (renal protective) CKD ACEi or ARB Heart failure ACEi/ARB + β-blocker + aldosterone antagonist Post-MI β-blocker + ACEi African-American CCB or thiazide (not ACEi first) Pregnancy Labetalol, nifedipine, methyldopa

Answer 15

1. Mean Definition: Average (sum of values ÷ number of values). Sensitive to outliers. 2. Median Definition: Middle value (50th percentile). Not affected by outliers. Best measure of central tendency in skewed distributions. 3. Mode Definition: Most frequently occurring value. Can be multiple modes or none. Used in categorical data.

Answer 16

4. Positive Skew (Right Skew) Tail goes right (towards high values). Mean > Median > Mode Example: Income distribution 5. Negative Skew (Left Skew) Tail goes left (towards low values). Mean < Median < Mode Example: Age at death in a nursing home USMLE Step 1 Tips MEMORIZE: Positive skew = Mean > Median > Mode Negative skew = Mean < Median < Mode Strategy: If asked about “best central tendency” in skewed data, pick median. Be careful with outliers—they distort the mean. Test Clue: If a question says "most patients had X, but a few had much higher values", think right skew, so mean > median.

Answer 17

If labs show ↑ TSH, ↓ T4, think primary hypothyroidism (e.g. Hashimoto). Hashimoto = Hürthle cells, increased risk of lymphoma If neonatal: Cretinism = intellectual disability, coarse facies, umbilical hernia TSH is most sensitive test for screening

Answer 18

Post-op neck surgery + hypocalcemia = iatrogenic hypoparathyroidism If you see hypocalcemia + hyperphosphatemia + ↓ PTH, it's hypoparathyroidism (vs. pseudohypoparathyroidism, which has ↑ PTH) DiGeorge clue = cardiac defects + hypocalcemia + facial anomalies

Answer 19

Thyroid Storm Life-threatening! Fever, tachyarrhythmia, agitation Treat with PTU + beta-blocker + corticosteroids + cooling 📌 USMLE Tips Graves = diffuse uptake on RAI scan Toxic adenoma = focal uptake Exophthalmos = only in Graves, not other causes PTU inhibits both TPO and peripheral T4→T3 conversion Methimazole = teratogenic in 1st trimester

Answer 20

Osteitis fibrosa cystica: Brown tumors (cystic bone spaces with fibrous tissue) 📌 USMLE Tips Primary = ↑ Ca²⁺ + ↑ PTH Secondary = ↓ Ca²⁺ + ↑ PTH Tertiary = ↑ PTH + normal/increased Ca²⁺ In CKD, phosphate retention leads to hypocalcemia → secondary hyperparathyroidism

Answer 21

Projectile vomiting + palpable mass + alkalosis in infant = pyloric stenosis Non-bilious vomiting = obstruction is before the duodenum Know the classic electrolyte pattern: ↓ Cl⁻, ↓ K⁺, ↑ pH Macrolide use in neonate or mother = strong clue Always correct metabolic alkalosis before surgery

Answer 22

Type: High anion gap metabolic acidosis ABG: ↓ pH, ↓ HCO₃⁻, ↓ PCO₂ (respiratory compensation) Tip: Look for Kussmaul breathing (deep, rapid), dehydration, fruity breath Clue labs: ↑ glucose, ↑ ketones, ↓ HCO₃⁻

Answer 23

Early: Respiratory alkalosis (direct medullary stimulation) Late: Mixed metabolic acidosis + respiratory alkalosis ABG: ↓ pH, ↓ PCO₂, ↓ HCO₃⁻ Tip: Look for tinnitus, confusion, and wide anion gap

Answer 24

Type: Metabolic alkalosis ABG: ↑ pH, ↑ HCO₃⁻, ↑ PCO₂ (compensatory hypoventilation) Tip: Classic post-op patient or bulimic with hypokalemia + hypochloremia

Answer 25

Type: Respiratory acidosis (chronic or acute) ABG: ↓ pH, ↑ PCO₂, ↑ HCO₃⁻ (if chronic compensation) Tip: Look for dyspnea, hypoxia, wheezing, and long smoking history

Answer 26

Type: Respiratory alkalosis ABG: ↑ pH, ↓ PCO₂, normal HCO₃⁻ Tip: Sudden dyspnea, pleuritic chest pain, tachypnea Classic: Patient just had surgery or long flight

Answer 27

Type: Non-anion gap metabolic acidosis ABG: ↓ pH, ↓ HCO₃⁻, ↓ PCO₂ Tip: Diarrhea = loss of HCO₃⁻ from GI tract

Answer 28

Normal: ↓ cortisol (suppressed) Cushing syndrome: No suppression → proceed to high-dose test

Answer 29

Helps differentiate Cushing disease vs. ectopic ACTH vs. adrenal tumor: Finding ACTH Level Cortisol Response Diagnosis ↓ ACTH No suppression Adrenal tumor ↑ ACTH Suppressed Cushing disease (pituitary adenoma) ↑ ACTH No suppression Ectopic ACTH (e.g., small cell lung cancer

Answer 30

USMLE Step 1 Tips Always start with low-dose dexamethasone + 24h urinary cortisol or late-night salivary cortisol If cortisol not suppressed → suspect Cushing syndrome High-dose test distinguishes between pituitary and ectopic sources: Pituitary (Cushing disease) → partial suppression Ectopic ACTH or adrenal tumor → no suppression Know the ACTH level interpretation alongside suppression: Low ACTH + high cortisol = adrenal source High ACTH + no suppression = ectopic High ACTH + suppression = pituitary

Answer 31

Dynein: High-Yield Facts 🔹 What it is: Motor protein that moves toward the minus end of microtubules (retrograde transport → to nucleus) 🔹 Function: Retrograde axonal transport (e.g. viruses like HSV, rabies) Ciliary and flagellar movement (along with axonemal dynein) Important in mitosis, organelle positioning, and intraflagellar transport USMLE Step 1 Tips "Retrograde transport" = dynein; "Anterograde" = kinesin Viruses like HSV, rabies, polio travel via dynein to the CNS Dynein mutations = think ciliary dysfunction, especially with recurrent respiratory infections + infertility + situs inversus In electron micrographs: absence of dynein arms in cilia → confirm Kartagener

Answer 32

Primary Ciliary Dyskinesia (Kartagener syndrome) Defective axonemal dynein arms → impaired ciliary motion Triad: Chronic sinusitis Bronchiectasis Situs inversus (due to disrupted left-right axis during embryogenesis) Infertility: immotile sperm or dysfunctional fallopian tube cilia

Answer 33

Erythema Multiforme (EM): High-Yield Facts 🔹 What it is: Immune-mediated skin reaction often triggered by infection or drugs Characterized by targetoid lesions (central dusky area, pale ring, red outer ring) 📋 **Causes (Mnemonic: HSV-MEDS) HSV (Herpes Simplex Virus) → most common trigger Mycoplasma pneumoniae Epstein-Barr Virus (EBV) Drugs (rare): sulfa, penicillin, phenytoin, barbiturates Type IV hypersensitivity reaction Cytotoxic T-cell-mediated response targeting keratinocytes with viral antigens

Answer 34

USMLE Step 1 Tips Classic presentation: Target lesions + recent HSV outbreak → think EM Don’t confuse with SJS/TEN — EM has minimal or no mucosal involvement, no full-thickness skin necrosis Type IV hypersensitivity = high-yield mechanism If asked for the most common trigger: answer HSV Mycoplasma-induced EM more common in children

Answer 35

Key Features Nephrotic syndrome (not nephritic) Thickened glomerular basement membrane (GBM) on light microscopy Subepithelial immune complex deposits → "spike and dome" appearance on electron microscopy Granular IF (IgG and C3) Primary (idiopathic): **** Autoantibodies to PLA2R (phospholipase A2 receptor) on podocytes → HIGH-YIELD! **** 🔹 Secondary causes: SLE (Class V) HBV/HCV Solid tumors (e.g. lung, colon, breast cancer) NSAIDs, penicillamine, syphilis

Answer 36

USMLE Step 1 Tips Nephrotic-range proteinuria (>3.5 g/day), hypoalbuminemia, edema, hyperlipidemia = classic nephrotic presentation PLA2R antibodies = specific for primary membranous nephropathy Think "spike and dome" pattern when you see subepithelial deposits If a middle-aged adult has nephrotic syndrome + solid tumor, suspect secondary membranous nephropathy Don’t confuse with membranoproliferative GN (which shows "tram-tracks" and more often nephritic features)

Answer 37

Condition Key USMLE Clue Pemphigus vulgaris Autoantibodies to desmoglein-3 (desmosomes) Stevens-Johnson Syndrome Drug reaction, mucosal involvement Toxic Epidermal Necrolysis Severe SJS spectrum, widespread full-thickness necrosis Staphylococcal Scalded Skin Syndrome (SSSS) Children, exfoliative toxin A targets desmoglein-1

Answer 38

Condition Key Feature Bullous pemphigoid Autoantibodies to hemidesmosomes (BP180) Dermatitis herpetiformis Associated with celiac disease, IgA in dermal papillae

Answer 39

USMLE Step 1 Tips: Pemphigus vulgaris = positive Nikolsky + oral mucosa involvement Bullous pemphigoid = negative Nikolsky + tense blisters If a child with widespread skin peeling + fever, think SSSS (not TEN, which is in adults) Nikolsky sign is a physical clue, not a disease—use it to narrow differential based on clinical context

High yield review 4 Flashcards

(64 cards)