Syndromic Autism Spectrum Disorder: Let Us Not Forget about Succinic Semialdehyde Dehydrogenase Deficiency. A Case Report with Literature Review.

We describe a girl with syndromic autism spectrum disorder (ASD), who at the end of the medical workup proved affected by a succinic semialdehyde dehydrogenase (SSADH) deficiency, a rare autosomal-recessive disorder of degradation of the γ-aminobutyric acid (GABA), that is, the most important central nervous system inhibitory neurotransmitter. The diagnosis of SSADH deficiency was made using a next-generation sequencing (NGS) multigene panel for neurological disorders and was confirmed by urinary organic acid analysis. Compared to the classic description of SSADH deficiency, our patient presented a less severe picture. In fact, she had no epilepsy, and her neuromotor signs were soft, and over time they became less evident. This case report emphasizes the importance of considering in a patient with syndromic ASD, the possible diagnosis of SSADH deficiency, even when all its typical signs are not present. Nowadays, the use of NGS multigene panels could facilitate the etiological diagnosis in individuals with syndromic ASD.