Impairment of SSADH activity is caused by mutations in the ALDH5A1 gene, which resides on chromosome 6p22 and encodes the SSADH enzyme, the deficiency of which results in a rare genetic disease, SSADH deficiency (SSADH-D) [5,6]. The gene discussed is ALDH5A1; the disease is hyperinsulinemic hypoglycemia, familial, 4.