Lipid Biochemistry USMLE Step 1 Practice Question
A 6-year-old boy presents with severe growth retardation, steatorrhea, and progressive neurodegeneration. Vital signs show BP 95/60, HR 102, RR 20, temperature 37.2°C, and SpO2 98% on room air. Laboratory studies reveal markedly elevated very long-chain fatty acids (VLCFAs) at 200 times the upper limit of normal, with normal very long-chain fatty acid β-oxidation. MRI demonstrates extensive cerebral white matter abnormalities. He denies recent infections. Which of the following is the most likely diagnosis?
Answer choices
- AX-linked adrenoleukodystrophy due to impaired peroxisomal β-oxidation of VLCFAsCorrect answer
- BZellweger syndrome with global peroxisomal dysfunction
- CMitochondrial fatty acid oxidation disorder affecting medium-chain fatty acids
- DPrimary carnitine deficiency affecting all fatty acid oxidation
- ENiemann-Pick disease type C with impaired cholesterol trafficking
- FKrabbe disease (galactocerebrosidase deficiency)
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