Medium-chain acyl-coenzyme A dehydrogenase (MCAD, EC 3.1.2.20) deficiency (OMIM 201450) is the most common disorder of fatty acid beta-oxidation caused by biallelic pathogenic ACADM gene (OMIM 607008) variants. The gene discussed is ACADM; the disease is hyperinsulinemic hypoglycemia, familial, 4.