A boy with a severe phenotype of succinic semialdehyde dehydrogenase deficiency.

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal recessive disorder affecting γ-aminobutyric acid degradation. We describe here a boy with a severe phenotype of SSADH deficiency. He was referred because of a developmental delay at 4 months of age. At the age of 8 months, severe seizures developed. The diagnosis of SSADH deficiency was confirmed by an increase in 4-hydroxybutyric acid and heteroallelic mutation in the ALDH5A1 gene. His seizures were successfully treated with high-dose phenobarbital, and the electroencephalogram (EEG) abnormalities were ameliorated. However, the patient showed a degenerative clinical course with severe neurological deficits. A magnetic resonance imaging (MRI) scan revealed abnormal high intensities in the putamina and caudate nuclei on T2-weighted images, followed by marked atrophic changes. The clinical manifestation of our patient indicates the wide variety of SSADH deficiency phenotypes.