Succinic semialdehyde dehydrogenase deficiency (SSADH-D, also called 4-hydroxybutyric aciduria, OMIM #271980) is an ultra-rare monogenic disorder of the γ-amino butyric acid (GABA) metabolism, with approximately 450 patients known to the literature (reviewed in [1,2]). This evidence concerns the gene ALDH5A1 and succinic semialdehyde dehydrogenase deficiency.