Recessive HADHB mutation results in the dysfunction of the beta-oxidation of fatty acids, leading to MTP deficiency, characterized in a severe heterogeneous syndrome, such as cardiomyopathy, recurrent Leigh-like encephalopathy, hepatopathy, and neonatal or unexpected infant death [27]. The gene discussed is HADHB; the disease is hyperinsulinemic hypoglycemia, familial, 4.