USMLE Clinical Medicine 1 — Questions and Answers
Question 1: A 65-year-old man presents with chest pain radiating to the left arm, diaphoresis, and ST elevation in leads II, III, and aVF. Which coronary artery is most likely occluded?
- Right coronary artery (RCA) (Correct answer)
- Left anterior descending artery (LAD)
- Left circumflex artery (LCx)
- Left main coronary artery
Correct answer: Right coronary artery (RCA)
ST elevation in leads II, III, and aVF indicates inferior STEMI, which is most commonly caused by occlusion of the right coronary artery (RCA) that supplies the inferior wall.
Question 2: A patient with hypertension develops a sudden severe headache described as 'the worst headache of my life.' What is the most important diagnosis to rule out?
- Subarachnoid hemorrhage (SAH) (Correct answer)
- Migraine
- Tension headache
- Hypertensive urgency
Correct answer: Subarachnoid hemorrhage (SAH)
A thunderclap headache (worst headache of life, maximal at onset) is the classic presentation of subarachnoid hemorrhage, typically from a ruptured berry aneurysm, requiring urgent CT and LP.
Question 3: A patient with type 2 diabetes presents with polydipsia, polyuria, and serum glucose of 650 mg/dL. Serum osmolality is 345 mOsm/kg. No ketones in urine. What is the diagnosis?
- Hyperosmolar hyperglycemic state (HHS) (Correct answer)
- Diabetic ketoacidosis (DKA)
- Diabetes insipidus
- SIADH
Correct answer: Hyperosmolar hyperglycemic state (HHS)
HHS is characterized by extreme hyperglycemia (>600 mg/dL), hyperosmolality (>320 mOsm/kg), and minimal ketosis, distinguishing it from DKA in type 2 diabetics with residual insulin.
Question 4: A 45-year-old woman with rheumatoid arthritis develops dry eyes, dry mouth, and parotid enlargement. Antibodies to SSA (Ro) and SSB (La) are positive. What is the diagnosis?
- Sjögren syndrome (Correct answer)
- SLE
- Sarcoidosis
- Amyloidosis
Correct answer: Sjögren syndrome
Sjögren syndrome is an autoimmune exocrinopathy characterized by lymphocytic infiltration of lacrimal and salivary glands, causing sicca symptoms (keratoconjunctivitis sicca and xerostomia) with anti-SSA/SSB antibodies.
Question 5: A patient presents with ascending weakness that started in the feet after a recent GI illness. CSF shows elevated protein with normal cell count (albuminocytologic dissociation). What is the diagnosis?
- Guillain-Barré syndrome (GBS) (Correct answer)
- Multiple sclerosis
- Amyotrophic lateral sclerosis
- Myasthenia gravis
Correct answer: Guillain-Barré syndrome (GBS)
GBS is an acute inflammatory demyelinating polyneuropathy triggered by molecular mimicry after infection (often Campylobacter jejuni), showing characteristic albuminocytologic dissociation in CSF.
Question 6: A patient with cirrhosis develops jaundice, ascites, and confusion. Asterixis is noted on exam. Serum ammonia is elevated. What is this complication called?
- Hepatic encephalopathy (Correct answer)
- Wernicke encephalopathy
- Spontaneous bacterial peritonitis
- Hepatorenal syndrome
Correct answer: Hepatic encephalopathy
Hepatic encephalopathy results from liver failure allowing ammonia and other toxins to reach the brain, causing asterixis (flapping tremor), confusion, and altered consciousness.
USMLE Clinical Medicine 1
A 65-year-old man presents with chest pain radiating to the left arm, diaphoresis, and ST elevation in leads II, III, and aVF.
Which coronary artery is most likely occluded?