A neonate develops recurrent hypoglycemia, hepatomegaly, and elevated plasma ammonia (380 μmol/L) without ketosis. Serum acylcarnitines show elevated C8 (octanoylcarnitine). The liver shows microvesicular steatosis on biopsy. Which diagnosis BEST fits this metabolic picture?
- A Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency ✓
- B Propionic acidemia
- C Methylmalonic acidemia
- D Glutaric aciduria type II (multiple acyl-CoA dehydrogenase deficiency, MADD)
Explanation
Elevated C8 (octanoylcarnitine) on acylcarnitine profile is the hallmark of MCAD (medium-chain acyl-CoA dehydrogenase) deficiency, the most common fatty acid oxidation disorder. Characteristic features include hypoketotic hypoglycemia (cannot produce ketones from fatty acids), hepatomegaly, microvesicular hepatic steatosis, and hyperammonemia during metabolic crises triggered by fasting or illness. Propionic and methylmalonic acidemias present with ketoacidosis and elevated C3 propionylcarnitine. Glutaric aciduria type II (MADD) shows multiple acylcarnitine elevations (C4-C18). MCAD is autosomal recessive and screened on newborn heel-prick via tandem mass spectrometry.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.