D-bifunctional protein (DBP) deficiency is a fatal autosomal recessive peroxisomal enzyme deficiency disease characterized by hypotonia, seizures, craniofacial dysmorphisms, psychomotor delay, deafness, and blindness in the neonatal period, with mortality generally occurring by two years of age [1]. The gene discussed is DBP; the disease is hyperinsulinemic hypoglycemia, familial, 4.