A 6-month-old infant presents with hypotonia, cardiomyopathy, and muscle weakness. Urine organic acids show elevated C8–C14 acylcarnitines. The enzyme defect is:

• A Very long-chain acyl-CoA dehydrogenase (VLCAD) ✓
• B Short-chain acyl-CoA dehydrogenase (SCAD)
• C Medium-chain acyl-CoA dehydrogenase (MCAD)
• D Long-chain hydroxyacyl-CoA dehydrogenase (LCHAD)

Explanation

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency presents in infancy with cardiomyopathy, hypotonia, and episodic hypoglycemia; C14:1 acylcarnitine is the characteristic marker. MCAD deficiency (the most common) presents later with hypoketotic hypoglycemia and C8 acylcarnitine. LCHAD presents with peripheral neuropathy and retinopathy. SCAD involves C4 acylcarnitines. The clinical triad of cardiomyopathy plus elevated C14 acylcarnitines points to VLCAD.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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