Among our MCADD cohort patients, we found three new ACADM mutations: two missense c.253G>C (p.Gly85Arg) and c.356T>A (p.Val119Asp), and one nonsense c.823G>T (p.Gly275*), which contribute to delineate the molecular genetic heterogeneity of MCADD. The gene discussed is ACADM; the disease is medium chain acyl-CoA dehydrogenase deficiency.