Take the full assessment for USMLE Step 1 preparation in 14 individually timed 30-minute blocks, then review every answer with full explanations. Bone Wizardry is independent and is not affiliated with or sanctioned by the USMLE program, FSMB, or NBME.
A 5-month-old infant is brought to the clinic for a protuberant abdomen and a recent seizure that occurred after a longer-than-usual interval between feeds. Examination reveals doll-like facies, thin extremities, and massive hepatomegaly without splenomegaly. Laboratory studies during a fast show a blood glucose of 32 mg/dL, lactate of 8.2 mmol/L, uric acid of 11.5 mg/dL, and triglycerides of 640 mg/dL. Administration of glucagon fails to raise the blood glucose. A liver biopsy shows hepatocytes distended with glycogen and lipid.
A deficiency of which of the following enzymes best accounts for this infant's findings?
AGlucose-6-phosphatase
BLysosomal acid alpha-1,4-glucosidase
CGlycogen debranching enzyme
DMuscle glycogen phosphorylase
EGlycogen branching enzyme
2026 Step 1 format
14 individually timed 30-minute blocks.
Up to 20 questions per block, a 55-minute pooled break allowance, and a 5-minute optional tutorial. Ending a block locks it, matching the current Step 1 flow.
