<unk>  (SSADHD), is a rare autosomal recessive disorder of the degradation pathway of the inhibitory neurotransmitter γ-aminobutyric acid, or GABA. The disorder has been identified in approximately 350 families, with a significant proportion being consanguineous families. The first case was identified in 1981 and published in a Dutch clinical chemistry journal that highlighted a number of neurological conditions such as delayed intellectual, motor, speech, and language as the most common manifestations. Later cases reported in the early 1990s began to show that hypotonia, hyporeflexia, seizures, and a nonprogressive ataxia were frequent clinical features as well.<unk>  is caused by an enzyme deficiency in GABA degradation. Under normal conditions, SSADH works with the enzyme GABA transaminase to convert GABA to<unk>  acid.<unk>  acid can then be utilized for energy production via the Krebs cycle. However, because of the deficiency, the final intermediate of the GABA degradation pathway,<unk><unk> , accumulates and cannot be oxidized to<unk>  acid and is therefore reduced to gamma-hydroxybutyric acid (GHB) by gamma-hydroxybutyric dehydrogenase. This causes elevations in GHB and is believed to be the trademark of this disorder and cause for the neurological manifestations seen.
Succinic semialdehyde dehydrogenase deficiency
Pyruvate dehydrogenase deficiency
2-Methylbutyryl-CoA dehydrogenase deficiency
3-Methylcrotonyl-CoA carboxylase deficiency
Malonyl-CoA decarboxylase deficiency
Glutaminase deficiency
Pyruvate kinase deficiency
Succinyl-CoA:3-oxoacid CoA transferase deficiency