Free MCCQE1 practice questions with answers

20 free MCCQE1 practice questions with answers and explanations

Open any question to see the answer. The full IMGQBank bank has more than 2,400 questions across 20 subjects, each with an explanation like these.

1. Question 1 · Cardiology

   A 65-year-old man presents with crushing chest pain radiating to the left arm, diaphoresis, and nausea for the past 2 hours. ECG shows ST elevation in leads II, III, and aVF. Which coronary artery is most likely occluded?

   • A.Left anterior descending artery
   • B.Right coronary artery
   • C.Left circumflex artery
   • D.Left main coronary artery
   Show the answer and explanation

   Correct answer: B. Right coronary artery

   ST elevation in leads II, III, and aVF indicates an inferior myocardial infarction. In approximately 85% of patients who have right-dominant coronary circulation, the right coronary artery (RCA) supplies the inferior wall of the left ventricle via the posterior descending artery (PDA). Therefore, RCA occlusion is the most common cause of inferior MI. Patients may also develop right ventricular infarction (check right-sided leads V4R) and bradycardia due to SA node involvement.

2. Question 2 · Pulmonology

   A 45-year-old woman with a 30-pack-year smoking history presents with progressive dyspnea, barrel chest, and pursed-lip breathing. PFTs show FEV1/FVC ratio of 0.55 and increased total lung capacity. CXR reveals hyperinflation with flattened diaphragms. What is the underlying pathophysiology?

   • A.Alveolar wall destruction with loss of elastic recoil
   • B.Bronchial wall thickening with mucus hypersecretion
   • C.Interstitial fibrosis with reduced lung compliance
   • D.Bronchospasm with reversible airway obstruction
   Show the answer and explanation

   Correct answer: A. Alveolar wall destruction with loss of elastic recoil

   This patient has emphysema, a subtype of COPD. The fundamental pathophysiology is destruction of alveolar walls caused by an imbalance between proteases (neutrophil elastase) and antiproteases (α1-antitrypsin). Smoking activates neutrophils and macrophages that release elastase, while simultaneously inactivating α1-antitrypsin. Alveolar wall destruction leads to: (1) Loss of elastic recoil → air trapping → hyperinflation and barrel chest, (2) Decreased surface area for gas exchange → dyspnea, (3) Loss of radial traction on small airways → expiratory collapse. PFTs show an obstructive pattern (decreased FEV1/FVC) with increased TLC and RV due to air trapping. Pursed-lip breathing is a compensatory mechanism to create back-pressure and prevent airway collapse.

3. Question 3 · Nephrology

   A 28-year-old man presents with cola-colored urine, periorbital edema, and hypertension 2 weeks after a sore throat. Urinalysis shows RBC casts and proteinuria. Serum complement C3 is low while C4 is normal. What is the most likely diagnosis?

   • A.IgA nephropathy
   • B.Post-streptococcal glomerulonephritis
   • C.Minimal change disease
   • D.Membranoproliferative glomerulonephritis
   Show the answer and explanation

   Correct answer: B. Post-streptococcal glomerulonephritis

   Post-streptococcal glomerulonephritis (PSGN) is a type III hypersensitivity reaction that occurs 1-3 weeks after Group A Streptococcal pharyngitis (or 3-6 weeks after skin infection). Immune complexes deposit in the glomerular basement membrane, activating complement via the alternative pathway (hence low C3 with normal C4). This causes a nephritic syndrome: hematuria (cola-colored urine from dysmorphic RBCs), RBC casts (pathognomonic for glomerulonephritis), mild-moderate proteinuria, periorbital edema, and hypertension. Light microscopy shows diffuse proliferative GN with neutrophil infiltration. Electron microscopy reveals characteristic 'subepithelial humps' (immune complex deposits). Treatment is supportive — most children recover fully, but adults may have residual renal impairment.

4. Question 4 · Endocrinology

   A 35-year-old woman presents with weight gain (15 lbs over 6 months), fatigue, constipation, dry skin, cold intolerance, and menorrhagia. Physical exam reveals delayed relaxation of deep tendon reflexes. Labs show TSH of 15 mIU/L (normal 0.4-4.0) and low free T4. Anti-TPO antibodies are markedly elevated. What is the most appropriate initial treatment?

   • A.Methimazole
   • B.Propylthiouracil (PTU)
   • C.Levothyroxine
   • D.Radioactive iodine (I-131) ablation
   Show the answer and explanation

   Correct answer: C. Levothyroxine

   This patient has Hashimoto's thyroiditis, the most common cause of hypothyroidism in iodine-sufficient areas. It is an autoimmune condition where anti-TPO and anti-thyroglobulin antibodies cause lymphocytic infiltration and gradual destruction of the thyroid gland. The elevated TSH represents the pituitary's attempt to stimulate the failing thyroid (primary hypothyroidism). Treatment is lifelong levothyroxine (synthetic T4) replacement. T4 is peripherally converted to the active T3 by deiodinases. The dose is typically 1.6 mcg/kg/day, titrated based on TSH levels checked every 6-8 weeks. Important considerations: take on an empty stomach 30-60 minutes before breakfast, avoid calcium/iron supplements within 4 hours, and elderly/cardiac patients should start at lower doses (25-50 mcg/day).

5. Question 5 · Neurology

   A 70-year-old man with history of atrial fibrillation (not on anticoagulation) presents with sudden onset of right-sided hemiplegia, right facial droop, and global aphasia. Symptoms began 90 minutes ago. Non-contrast CT head is negative for hemorrhage. Blood glucose is 110 mg/dL. What is the most appropriate next step?

   • A.Aspirin 325 mg orally
   • B.IV alteplase (tPA)
   • C.IV heparin infusion
   • D.Emergent carotid endarterectomy
   Show the answer and explanation

   Correct answer: B. IV alteplase (tPA)

   This patient presents with an acute ischemic stroke (likely cardioembolic from atrial fibrillation) within the 4.5-hour treatment window. IV alteplase (tPA) is the first-line thrombolytic therapy for eligible patients presenting within 4.5 hours of symptom onset. Key eligibility criteria: (1) Clinical diagnosis of ischemic stroke with measurable neurological deficit, (2) CT negative for hemorrhage, (3) Onset within 4.5 hours, (4) No absolute contraindications (recent surgery, active bleeding, platelet count <100K, INR >1.7). The dose is 0.9 mg/kg (max 90 mg), with 10% given as IV bolus and the remainder infused over 60 minutes. Blood pressure must be maintained <185/110 before and <180/105 after tPA administration. For large vessel occlusions, mechanical thrombectomy may be added up to 24 hours after onset.

6. Question 6 · Gastroenterology

   A 50-year-old man with a 20-year history of heavy alcohol use presents with jaundice, ascites, spider angiomata, and palmar erythema. Labs show AST 120, ALT 60 (AST:ALT ratio 2:1), total bilirubin 4.5 mg/dL, albumin 2.1 g/dL, INR 2.3, and platelet count 75,000. Which finding is the BEST indicator of synthetic liver dysfunction?

   • A.Elevated AST and ALT with 2:1 ratio
   • B.Elevated total bilirubin
   • C.Prolonged INR and low albumin
   • D.Thrombocytopenia (low platelets)
   Show the answer and explanation

   Correct answer: C. Prolonged INR and low albumin

   Hepatic synthetic function refers specifically to the liver's ability to produce proteins. The two best clinical indicators are: (1) PT/INR — the liver synthesizes clotting factors I (fibrinogen), II (prothrombin), V, VII, IX, and X. Factor VII has the shortest half-life (~6 hours), making PT/INR the most sensitive early marker of synthetic dysfunction. (2) Serum albumin — produced exclusively by hepatocytes with a half-life of ~21 days. Low albumin reflects chronic synthetic impairment. Both PT/INR and albumin are incorporated into the Child-Pugh classification (along with bilirubin, ascites, and encephalopathy) and the MELD score (which uses INR, bilirubin, and creatinine) to assess severity of liver disease and prioritize transplant listing.

7. Question 7 · Hematology & Oncology

   A 25-year-old African American man develops severe back pain, jaundice, and dark urine 2 days after starting primaquine for malaria prophylaxis. Labs show hemoglobin 7.5 g/dL (baseline 14), reticulocyte count 8%, LDH 850 U/L, haptoglobin <10 mg/dL, and indirect bilirubin 4.2 mg/dL. Peripheral smear shows bite cells and Heinz bodies. What is the most likely diagnosis?

   • A.Autoimmune hemolytic anemia (AIHA)
   • B.G6PD deficiency
   • C.Hereditary spherocytosis
   • D.Paroxysmal nocturnal hemoglobinuria (PNH)
   Show the answer and explanation

   Correct answer: B. G6PD deficiency

   G6PD (glucose-6-phosphate dehydrogenase) deficiency is the most common human enzymopathy, affecting ~400 million people worldwide. It is X-linked recessive, most prevalent in African American males (A- variant), Mediterranean populations (Mediterranean variant — more severe), and Southeast Asians. G6PD catalyzes the first step of the hexose monophosphate shunt (pentose phosphate pathway), generating NADPH. NADPH is essential for regenerating reduced glutathione, which protects RBCs from oxidative damage. When exposed to oxidant stressors (primaquine, dapsone, sulfonamides, nitrofurantoin, fava beans, infections), the RBCs cannot neutralize reactive oxygen species. This causes: (1) Heinz bodies — denatured hemoglobin aggregates visible with crystal violet stain, (2) Bite cells — formed when splenic macrophages 'bite out' Heinz bodies from RBCs, (3) Intravascular and extravascular hemolysis. Diagnosis: G6PD enzyme assay (but test AFTER acute episode resolves, as reticulocytes have higher G6PD levels and may give false-normal results during hemolysis).

8. Question 8 · Rheumatology

   A 30-year-old woman presents with malar (butterfly) rash sparing the nasolabial folds, painful swollen joints in both hands, oral ulcers, and photosensitivity. Labs show ANA positive (1:640, homogeneous pattern), anti-dsDNA positive, anti-Smith positive, low C3 and C4, and 24-hour urine protein of 4.2 g. Renal biopsy shows involvement of >50% of glomeruli with wire-loop lesions. What is the class of lupus nephritis?

   • A.Class I — Minimal mesangial
   • B.Class II — Mesangial proliferative
   • C.Class III — Focal proliferative
   • D.Class IV — Diffuse proliferative
   Show the answer and explanation

   Correct answer: D. Class IV — Diffuse proliferative

   Class IV diffuse proliferative lupus nephritis is the MOST COMMON and MOST SEVERE form of lupus nephritis. Key diagnostic features: (1) >50% of glomeruli involved (distinguishing it from Class III which is <50%), (2) Wire-loop lesions on light microscopy (thickened capillary walls due to massive subendothelial immune complex deposits), (3) 'Full house' immunofluorescence pattern (IgG, IgA, IgM, C3, C1q deposits — all positive), (4) Subendothelial deposits on electron microscopy. Clinical presentation includes both nephrotic features (heavy proteinuria, edema) AND nephritic features (hematuria, RBC casts, hypertension, renal insufficiency). Anti-dsDNA levels correlate with disease activity and often rise before flares. Low complement (C3, C4) reflects consumption by immune complexes. Treatment requires aggressive immunosuppression: induction with mycophenolate mofetil (MMF) or IV cyclophosphamide + high-dose corticosteroids, followed by maintenance with MMF or azathioprine.

9. Question 9 · Infectious Disease

   A 32-year-old HIV-positive man with CD4 count of 45 cells/μL (not on ART) presents with 2 weeks of progressively worsening headache, fever, neck stiffness, and confusion. Lumbar puncture shows: opening pressure 32 cm H2O (elevated), WBC 20 (lymphocytic predominance), glucose 30 mg/dL (low), protein 80 mg/dL (elevated). India ink preparation is positive showing encapsulated yeast. Cryptococcal antigen is positive at 1:1024. What is the recommended treatment?

   • A.Fluconazole 400 mg daily alone
   • B.Liposomal amphotericin B + flucytosine induction, then fluconazole
   • C.Voriconazole
   • D.Caspofungin
   Show the answer and explanation

   Correct answer: B. Liposomal amphotericin B + flucytosine induction, then fluconazole

   Cryptococcal meningitis is the most common fungal meningitis in HIV/AIDS patients, typically occurring when CD4 <100 cells/μL. Cryptococcus neoformans is an encapsulated yeast found in pigeon droppings and soil. The polysaccharide capsule is its major virulence factor, inhibiting phagocytosis. Treatment follows a three-phase protocol: (1) INDUCTION (2 weeks): Liposomal amphotericin B (3-4 mg/kg/day IV) + flucytosine (25 mg/kg QID orally). This combination is synergistic — amphotericin disrupts the cell membrane while flucytosine inhibits DNA/RNA synthesis. (2) CONSOLIDATION (8 weeks): Fluconazole 400 mg/day orally. (3) MAINTENANCE: Fluconazole 200 mg/day until CD4 >100 for ≥1 year on ART with undetectable viral load. Critical: Elevated intracranial pressure (>25 cm H2O) requires daily therapeutic lumbar punctures to remove CSF and reduce pressure — this is the major cause of early mortality. ART should be DELAYED 4-6 weeks after starting antifungal therapy to prevent immune reconstitution inflammatory syndrome (IRIS).

10. Question 10 · Nephrology

    A 55-year-old woman with type 2 diabetes and microalbuminuria (urine albumin 180 mg/day) is started on lisinopril (an ACE inhibitor) for renal protection. Two weeks later, she develops a persistent dry cough that significantly affects her sleep. Which drug class provides equivalent renoprotective benefits without the cough?

    • A.Amlodipine (calcium channel blocker)
    • B.Losartan (angiotensin receptor blocker)
    • C.Metoprolol (beta blocker)
    • D.Hydrochlorothiazide (thiazide diuretic)
    Show the answer and explanation

    Correct answer: B. Losartan (angiotensin receptor blocker)

    ACE inhibitors cause a dry cough in 5-20% of patients (more common in women and Asian patients) due to accumulation of bradykinin and substance P in the lungs. ACE normally degrades bradykinin; when ACE is inhibited, bradykinin accumulates, stimulating C-fibers and causing cough. Angiotensin receptor blockers (ARBs) like losartan block the angiotensin II type 1 (AT1) receptor directly, providing the same downstream effects: (1) Efferent arteriolar dilation → reduced intraglomerular pressure → reduced proteinuria, (2) Decreased aldosterone secretion → reduced sodium retention, (3) Decreased mesangial cell proliferation and fibrosis. Crucially, ARBs do NOT inhibit ACE and therefore do not cause bradykinin accumulation — hence no cough. Landmark trials (RENAAL, IDNT) demonstrated that ARBs reduce progression of diabetic nephropathy. Important: ACEi and ARBs should NOT be combined (ONTARGET trial showed increased adverse effects without additional benefit).

11. Question 11 · Obstetrics & Gynecology

    A 28-year-old primigravida at 34 weeks gestation presents with severe headache, blurred vision, and right upper quadrant pain. Blood pressure is 168/112 mmHg (previously normal). Labs: platelets 85,000, AST 280, ALT 310, LDH 650, creatinine 1.4, and urinalysis shows 3+ proteinuria. What is the most appropriate immediate management?

    • A.Oral labetalol and outpatient follow-up in 1 week
    • B.IV magnesium sulfate and IV antihypertensive therapy
    • C.Immediate cesarean delivery without stabilization
    • D.IV furosemide for fluid overload
    Show the answer and explanation

    Correct answer: B. IV magnesium sulfate and IV antihypertensive therapy

    This patient has severe preeclampsia with features of HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets). The right upper quadrant pain suggests hepatic capsule distension from periportal hemorrhage and inflammation. Immediate management priorities: (1) IV MAGNESIUM SULFATE — the gold standard for seizure prophylaxis (loading dose 4-6g IV over 20 minutes, then 1-2g/hour maintenance). Magnesium acts as a CNS depressant and vasodilator. Monitor for toxicity: loss of deep tendon reflexes (first sign), respiratory depression, cardiac arrest. Antidote: IV calcium gluconate. (2) IV ANTIHYPERTENSIVE therapy for BP ≥160/110 to prevent stroke: IV labetalol (20mg bolus, can escalate) OR IV hydralazine (5-10mg) OR oral nifedipine (10mg immediate release). Target BP: 140-150/90-100 mmHg. (3) Administer betamethasone for fetal lung maturity (34 weeks). (4) Plan for delivery within 24-48 hours after stabilization — delivery is the definitive treatment. At ≥34 weeks with severe features, delivery should not be delayed for corticosteroid benefit.

12. Question 12 · Pediatrics

    A 2-year-old boy is brought to the ED at 2 AM with a barking cough, inspiratory stridor at rest, and mild chest wall retractions. He had rhinorrhea and low-grade fever for 2 days. He is alert, drinking fluids, and has oxygen saturation of 95%. AP neck X-ray shows symmetric subglottic narrowing (steeple sign). What is the most likely causative organism?

    • A.Haemophilus influenzae type b
    • B.Parainfluenza virus (types 1 and 2)
    • C.Staphylococcus aureus
    • D.Respiratory syncytial virus (RSV)
    Show the answer and explanation

    Correct answer: B. Parainfluenza virus (types 1 and 2)

    Croup (acute laryngotracheobronchitis) is the most common cause of acute upper airway obstruction in children aged 6 months to 3 years, with peak incidence in the fall and early winter. Parainfluenza virus types 1 and 2 account for approximately 75% of cases. The virus causes inflammation and edema of the subglottic region (the narrowest part of the pediatric airway), producing the classic triad: (1) Barking/seal-like cough, (2) Inspiratory stridor, (3) Hoarseness. Symptoms characteristically worsen at night due to natural cortisol nadir. The 'steeple sign' on AP neck X-ray reflects symmetric subglottic narrowing (loss of the normal shouldering of the subglottic airway). Treatment is based on severity: MILD (barking cough, no stridor at rest): single dose oral dexamethasone (0.6 mg/kg). MODERATE (stridor at rest, retractions): dexamethasone + nebulized racemic epinephrine (α-adrenergic vasoconstriction reduces mucosal edema). SEVERE (significant distress, altered consciousness): same as moderate + preparation for possible intubation.

13. Question 13 · Psychiatry

    A 22-year-old college student is brought by her roommate for evaluation. She has had 5 episodes of major depression over the past 3 years, each lasting 2-3 months with suicidal ideation. Between depressive episodes, she has had at least 3 periods lasting 4-5 days each where she felt unusually energetic, slept only 3 hours/night, talked rapidly, had racing thoughts, and started multiple ambitious projects — but she continued attending classes and never required hospitalization during these periods. What is the most likely diagnosis?

    • A.Bipolar I disorder
    • B.Bipolar II disorder
    • C.Cyclothymic disorder
    • D.Major depressive disorder with mixed features
    Show the answer and explanation

    Correct answer: B. Bipolar II disorder

    Bipolar II disorder is defined by the presence of at least ONE hypomanic episode AND at least ONE major depressive episode, with NO history of full manic episodes. The critical distinction between mania and hypomania: HYPOMANIA (≥4 days): elevated/irritable mood with increased energy, plus ≥3 symptoms (decreased sleep need, pressured speech, racing thoughts, distractibility, increased goal-directed activity, risky behavior) — but WITHOUT marked functional impairment, psychotic features, or hospitalization. MANIA (≥7 days or any duration with hospitalization): same symptoms but WITH marked impairment, psychosis, or hospitalization needed. Bipolar II is often misdiagnosed as MDD because patients tend to seek help during depressive episodes and may not recognize hypomania as pathological (they may feel productive and creative). This is clinically important because antidepressant monotherapy in bipolar II can trigger hypomania/mania — mood stabilizers (lithium, lamotrigine, valproate) are the foundation of treatment.

14. Question 14 · Dermatology

    A 45-year-old man presents with a lesion on his upper back that his wife noticed has been changing over the past 8 months. Examination reveals a 12mm asymmetric plaque with irregular borders, variegated coloring (brown, black, red, and blue areas), and a recent history of spontaneous bleeding. He has a history of multiple sunburns in childhood. What is the next best step in management?

    • A.Reassurance and sunscreen counseling
    • B.Shave biopsy of the most raised area
    • C.Excisional biopsy with 1-3mm margins
    • D.Wide local excision with 2cm margins
    Show the answer and explanation

    Correct answer: C. Excisional biopsy with 1-3mm margins

    This lesion demonstrates all ABCDEs of melanoma: Asymmetry, Border irregularity, Color variegation (multiple colors), Diameter >6mm (12mm), and Evolution (changing over 8 months with bleeding). The next step is EXCISIONAL BIOPSY with narrow (1-3mm) margins to include the entire lesion and subcutaneous fat for accurate histopathological assessment. The critical measurement is Breslow depth (thickness in millimeters from the granular layer to the deepest point of invasion), which determines: (1) Surgical re-excision margins: ≤1mm → 1cm margin, 1.01-2mm → 1-2cm margin, >2mm → 2cm margin. (2) Need for sentinel lymph node biopsy (recommended for Breslow depth ≥0.8mm or ≥1mm with ulceration). (3) Need for adjuvant therapy (immunotherapy with checkpoint inhibitors for stage III/IV). Risk factors include: UV exposure (especially childhood sunburns), fair skin, family history, numerous moles (>50), dysplastic nevi, and immunosuppression.

15. Question 15 · Surgery

    A 55-year-old man presents with acute onset severe epigastric pain radiating straight to the back, nausea, and vomiting after a heavy fatty meal. He has a history of gallstones. On exam, he is writhing in pain, has epigastric tenderness with guarding, and diminished bowel sounds. Labs: amylase 850 U/L, lipase 1200 U/L, WBC 18,000, glucose 220 mg/dL, LDH 400 U/L, AST 280 U/L. Which of the following Ranson criteria can be determined at the time of admission?

    • A.Serum calcium < 8 mg/dL
    • B.PaO2 < 60 mmHg
    • C.Age > 55 years
    • D.Base deficit > 4 mEq/L
    Show the answer and explanation

    Correct answer: C. Age > 55 years

    Ranson's criteria predict severity and mortality in acute pancreatitis using 11 parameters assessed at two time points. AT ADMISSION (mnemonic: GA LAW): (1) Glucose >200 mg/dL ✓ (this patient: 220), (2) Age >55 years ✓ (this patient: 55), (3) LDH >350 IU/L ✓ (this patient: 400), (4) AST >250 IU/L ✓ (this patient: 280), (5) WBC >16,000/μL ✓ (this patient: 18,000). AT 48 HOURS (mnemonic: C HOBBS): (1) Calcium <8 mg/dL, (2) Hematocrit fall >10%, (3) O2 (PaO2) <60 mmHg, (4) BUN increase >5 mg/dL, (5) Base deficit >4 mEq/L, (6) Sequestration (fluid needs) >6L. Scoring: 0-2 criteria = mild (mortality ~1%), 3-4 = moderate (mortality ~15%), 5-6 = severe (mortality ~40%), 7-8 = critical (mortality ~100%). This patient already meets 5 admission criteria (GA LAW all positive), indicating severe pancreatitis requiring ICU admission, aggressive IV fluid resuscitation (250-500 mL/hour of lactated Ringer's), pain management, and monitoring for complications (necrosis, pseudocyst, abscess, organ failure).

16. Question 16 · Orthopedics

    A 78-year-old osteoporotic woman trips and falls on her right side. She is unable to bear weight. Examination shows the right leg is shortened and externally rotated. X-ray confirms a displaced (Garden type III) femoral neck fracture. She was independently ambulatory prior to the fall with no significant comorbidities. What is the preferred surgical treatment?

    • A.Conservative management with bed rest and traction
    • B.Internal fixation with cannulated screws
    • C.Hemiarthroplasty or total hip arthroplasty
    • D.Dynamic hip screw (DHS) fixation
    Show the answer and explanation

    Correct answer: C. Hemiarthroplasty or total hip arthroplasty

    Displaced femoral neck fractures (Garden III and IV) in elderly patients are best treated with arthroplasty rather than internal fixation. The femoral head blood supply comes primarily from the medial femoral circumflex artery via retinacular vessels that run along the femoral neck — displacement disrupts these vessels, creating a high risk of avascular necrosis (AVN) and nonunion with fixation alone. Choice between hemiarthroplasty (replaces femoral head only) and total hip arthroplasty (THA — replaces both femoral head and acetabulum) depends on patient factors: HEMIARTHROPLASTY: for less active, older patients (>80) or those with significant comorbidities — simpler procedure, shorter operative time, lower dislocation risk. TOTAL HIP ARTHROPLASTY: for active, healthy patients with good life expectancy and no pre-existing acetabular disease — better functional outcomes, lower reoperation rates, but higher dislocation risk and longer surgery. Key principle: surgery should ideally be performed within 24-48 hours of injury to reduce mortality, delirium, and complications.

17. Question 17 · Ophthalmology

    A 62-year-old man with poorly controlled type 2 diabetes (HbA1c 9.8%) for 18 years presents with gradually progressive painless vision loss in both eyes over several months. Fundoscopic examination reveals neovascularization at the optic disc and elsewhere, multiple dot-blot hemorrhages, hard exudates, cotton wool spots, and venous beading. What is the most appropriate treatment?

    • A.Topical timolol (beta blocker eye drops)
    • B.Pan-retinal photocoagulation (PRP)
    • C.Intravitreal dexamethasone implant
    • D.Oral acetazolamide (carbonic anhydrase inhibitor)
    Show the answer and explanation

    Correct answer: B. Pan-retinal photocoagulation (PRP)

    This patient has proliferative diabetic retinopathy (PDR), the most vision-threatening stage, characterized by NEOVASCULARIZATION — new, fragile blood vessel growth driven by retinal ischemia and VEGF (vascular endothelial growth factor) release. These new vessels are prone to hemorrhage (causing vitreous hemorrhage and sudden vision loss) and can cause tractional retinal detachment. Staging of diabetic retinopathy: (1) Mild NPDR: microaneurysms only, (2) Moderate NPDR: dot-blot hemorrhages, hard exudates, cotton wool spots, (3) Severe NPDR ('4-2-1 rule': hemorrhages in 4 quadrants, venous beading in 2 quadrants, IRMA in 1 quadrant), (4) PDR: NEOVASCULARIZATION ± vitreous hemorrhage ± retinal detachment. Treatment: PAN-RETINAL PHOTOCOAGULATION (PRP) — laser burns applied to the peripheral ischemic retina (1,200-1,600 spots), destroying ischemic tissue to reduce VEGF production. This causes regression of neovascularization in ~60% of cases. Anti-VEGF injections (ranibizumab, aflibercept, bevacizumab) are increasingly used as first-line or adjunctive therapy. All diabetic patients need annual dilated eye exams, tight glycemic control (HbA1c <7%), and BP control.

18. Question 18 · Pediatrics

    A newborn develops visible jaundice within the first 18 hours of life. The mother is blood type O, Rh-negative, and the baby is blood type A, Rh-positive. Direct Coombs test (DAT) on the baby's blood is strongly positive. Total bilirubin is 12 mg/dL and rising rapidly. What is the primary mechanism of hemolysis?

    • A.Intrinsic RBC membrane defect causing osmotic fragility
    • B.Maternal IgG antibodies crossing the placenta and opsonizing fetal RBCs
    • C.Neonatal sepsis causing disseminated intravascular coagulation
    • D.Physiologic immaturity of hepatic UDP-glucuronyl transferase
    Show the answer and explanation

    Correct answer: B. Maternal IgG antibodies crossing the placenta and opsonizing fetal RBCs

    This is hemolytic disease of the fetus and newborn (HDFN) caused by BOTH ABO and Rh incompatibility. The mechanism: the mother (type O, Rh-negative) has naturally occurring IgG anti-A antibodies (ABO incompatibility) AND may have developed anti-D antibodies from prior sensitization (Rh incompatibility). IgG (but not IgM) crosses the placenta via FcRn receptors and binds to the corresponding antigens on fetal RBCs. These antibody-coated (opsonized) RBCs are then destroyed by fetal/neonatal splenic macrophages via Fc receptor-mediated phagocytosis (extravascular hemolysis). The positive direct Coombs test (DAT) confirms the presence of maternal antibodies bound to the baby's RBCs. Key clinical points: (1) Jaundice within 24 hours = ALWAYS pathological, (2) Rising bilirubin can cause kernicterus (bilirubin encephalopathy) — unconjugated bilirubin crosses the blood-brain barrier and deposits in basal ganglia and brainstem nuclei, (3) Treatment: phototherapy (converts unconjugated bilirubin to water-soluble isomers for renal excretion), exchange transfusion if severe, IV immunoglobulin. Prevention of Rh sensitization: RhoGAM (anti-D immunoglobulin) given to Rh-negative mothers at 28 weeks and within 72 hours postpartum.

19. Question 19 · Infectious Disease

    A 19-year-old college freshman presents with fever (38.8°C), severe sore throat, cervical lymphadenopathy, tonsillar exudates, fatigue, and a palpable spleen tip. CBC shows atypical lymphocytes (10%). Monospot (heterophile antibody) test is positive. An outside urgent care provider prescribed amoxicillin 3 days ago. The patient now has a diffuse, bilateral, non-pruritic maculopapular rash on the trunk and extremities. What is the most likely explanation for the rash?

    • A.Type I (IgE-mediated) penicillin allergy causing urticaria
    • B.Drug-induced maculopapular eruption specific to EBV + aminopenicillins
    • C.Stevens-Johnson syndrome from amoxicillin
    • D.Viral exanthem from EBV itself, unrelated to amoxicillin
    Show the answer and explanation

    Correct answer: B. Drug-induced maculopapular eruption specific to EBV + aminopenicillins

    Infectious mononucleosis (caused by Epstein-Barr virus, EBV) produces a characteristic diffuse maculopapular rash in approximately 80-100% of patients who are given aminopenicillins (ampicillin or amoxicillin). This is NOT a true penicillin allergy — the mechanism is thought to involve transient altered immune regulation during acute EBV infection, possibly due to polyclonal B-cell activation leading to aberrant immune complex formation with the drug. The rash typically appears 7-10 days after starting the antibiotic, is diffuse and bilateral, and resolves without complications. Important clinical points: (1) This reaction does NOT indicate a lifelong penicillin allergy — penicillins can be safely used in the future, (2) EBV is transmitted via saliva ('kissing disease'), incubation 4-6 weeks, (3) Atypical lymphocytes are reactive CD8+ T cells responding to EBV-infected B cells, (4) Heterophile antibodies are IgM antibodies that cross-react with horse/sheep RBCs (monospot test), (5) Avoid contact sports for at least 3-4 weeks due to risk of splenic rupture, (6) EBV is associated with Burkitt lymphoma (t(8;14) c-myc), nasopharyngeal carcinoma, Hodgkin lymphoma, and post-transplant lymphoproliferative disorder (PTLD).

20. Question 20 · Surgery

    A 48-year-old woman undergoes total thyroidectomy for papillary thyroid carcinoma. On postoperative day 1, she is noted to have a hoarse, breathy voice and difficulty projecting her voice. Flexible laryngoscopy shows the left vocal cord is fixed in the paramedian position. Which nerve was most likely injured during surgery?

    • A.External branch of the superior laryngeal nerve
    • B.Recurrent laryngeal nerve
    • C.Internal branch of the superior laryngeal nerve
    • D.Hypoglossal nerve (CN XII)
    Show the answer and explanation

    Correct answer: B. Recurrent laryngeal nerve

    The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve (CN X) and is the most commonly injured nerve during thyroidectomy (reported incidence 1-2% for experienced surgeons, up to 14% in re-operations). It runs in or near the tracheoesophageal groove, in close proximity to the inferior thyroid artery and the ligament of Berry (posterior suspensory ligament of the thyroid). The RLN innervates ALL intrinsic laryngeal muscles EXCEPT the cricothyroid: (1) Posterior cricoarytenoid (PCA) — the ONLY abductor of the vocal cord, (2) Lateral cricoarytenoid — adductor, (3) Thyroarytenoid — adductor/tensor, (4) Interarytenoid — adductor, (5) Vocalis — fine tension adjustment. Injury consequences: UNILATERAL RLN injury → vocal cord paralysis in paramedian position → hoarseness, breathy voice, difficulty projecting voice, aspiration risk. BILATERAL RLN injury → both cords fixed in paramedian/adducted position → stridor, airway obstruction, respiratory distress requiring emergent tracheostomy. Anatomical note: The LEFT RLN loops under the aortic arch and ascends in the tracheoesophageal groove (longer course = more vulnerable). The RIGHT RLN loops under the right subclavian artery (shorter, slightly less vulnerable). During thyroidectomy, the RLN is identified and preserved by dissecting along the tracheoesophageal groove, often using intraoperative nerve monitoring (IONM).