Succinic semialdehyde dehydrogenase (SSADH) deficiency, also known as 4-hydroxybutyric aciduria (4-HBA), is an autosomal recessive inborn error of metabolism. Clinical features include intellectual disability with prominent deficits in expressive language, hypotonia, nonprogressive ataxia, and hyporeflexia. The causative gene is aldehyde dehydrogenase 5 family, member A1 (ALDH5A1) encoding SSADH. SSADH is deficient in affected individuals impairing the formation of succinic acid from succinic semialdehyde and leading to the increased production of 4-HBA.
