CPT2 and hyperinsulinemic hypoglycemia, familial, 4: L-Palmitoylcarnitine and octadecenylcarnitine, involved in oxidation of fatty acids, are a long-chain acyl fatty acid esters of carnitine, and L-palmitoylcarnitine accumulates in the cytosol and serum of patients suffering from mitochondrial carnitine palmitoyltransferase II deficiency.