Succinic Semialdehyde Dehydrogenase Deficiency
Succinic semialdehyde dehydrogenase (SSADH) deficiency presents with intellectual disability, disproportionate deficit in expressive language, hypotonia, ataxia, and seizures.1,2 (1 Pearl et al 2011; 2 Vogel et al 2012). A diagnosis of autism spectrum disorder frequently occurs, correlated with neuropsychiatric morbidity (ADHD, OCD, PDD). 1,3 The biochemical hallmark, γ-hydroxybutyric acid (GHB), is elevated in physiological fluids, as is γ-aminobutyrate (GABA) in cerebrospinal fluid (CSF).4,5 Both species are neuroactive. Clinical manifestations are universally present in early childhood, although diagnosis delayed to adulthood has been reported.6 Acute decompensation or complications relate primarily to seizures, intercurrent illnesses sometimes associated with respiratory dysfunction in the setting of hypotonia, or adverse medication responses. Diagnostic confirmation requires urine organic acid analysis (increased GHB) with confirmation via enzyme assay (white cells) and/or molecular characterization of the aldehyde dehydrogenase 5a1 (ALDH5A1) gene.