Succinic semialdehyde dehydrogenase deficiency: low excretion of metabolites in a neonate.

A neonate at risk for succinic semialdehyde dehydrogenase deficiency was investigated on day 1. The urine level of 4-hydroxybutyrate was only slightly elevated (23 mumol/mmol of creatinine; controls 1.6-14, n = 18). This value was considerably less than those found for older children with succinic semialdehyde dehydrogenase deficiency and made interpretation of the result uncertain. The diagnosis of succinic semialdehyde dehydrogenase deficiency was confirmed by enzyme assay, and repeat urine testing showed a steady increase in the level of 4-hydroxybutyrate to 359 mumol/mmol at 6 months.