CPT II deficiency has been clinically classified into three phenotypes: (1) a lethal neonatal form associated with cardiomyopathy; (2) a hypoglycemic form, manifesting mainly during infancy and early childhood, that provokes hypoglycemia, Reye-like encephalopathy, and, in the most severe cases, cardiopulmonary arrest; and (3) a myopathic form characterized by recurrent rhabdomyolysis with onset in adolescence or later. Here, CPT2 is linked to hyperinsulinemic hypoglycemia, familial, 4.