Even in persons with primary systemic carnitine deficiency (or: OCTN2 deficiency, OMIM:#212140), who exhibit extremely low‐plasma (<5 μmol/L) carnitine concentrations, clinical manifestations range widely; from severe hypoglycemia early in life, development of cardiomyopathy later in life, to absence of symptoms.34, 35. The gene discussed is SLC22A5; the disease is hyperinsulinemic hypoglycemia, familial, 4.