A patient has hypoketotic hypoglycemia with accumulation of 16-carbon fatty acids such as palmitate. Which deficiency best explains this?

• A. MCAD deficiency
• B. Long-chain acyl-CoA dehydrogenase deficiency
• C. CPT I deficiency
• D. Carnitine deficiency

Answer: (B)

When fasting, the body relies on fatty acids oxidized in mitochondria to provide energy and to generate ketone bodies. If a step in beta-oxidation is impaired, acetyl-CoA production drops, so ketone formation falls and hypoglycemia can occur without ketones—hypoketotic hypoglycemia. The long-chain fatty acids, like palmitate (C16), require the enzyme long-chain acyl-CoA dehydrogenase to initiate their beta-oxidation. A deficiency here blocks oxidation of these long-chain fatty acids, causing their accumulation and preventing ketogenesis. This pattern fits best with long-chain acyl-CoA dehydrogenase deficiency, explaining both the buildup of long-chain fatty acids and the hypoketotic hypoglycemia.