Carnitine transfers long-chain fatty acids into the mitochondria, making them available for ß-oxidation and ketogenesis by means of enzymes and transporters such as OCTN2 carnitine transporter (involved in primary carnitine deficiency, ORPHA158), carnitine palmitoyltransferase-1 (CPT1, <1/1,000,000; ORPHA156), carnitine/acylcarnitine translocase (CACT, <1/1,000,000; ORPHA159), and carnitine palmitoyltransferase-2 (CPT2, <1/1,000,000; ORPHA157). This evidence concerns the gene CPT2 and systemic primary carnitine deficiency disease.