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  • Updated 12.22.2022
  • Released 03.21.1994
  • Expires For CME 12.22.2025

GABA-transaminase deficiency

Introduction

Overview

GABA-transaminase deficiency is a rare GABA metabolism disorder that combines neonatal encephalopathy, hypotonia, and epilepsy. In this article, the authors review this enigmatic pediatric neurotransmitter disorder. Patients have manifested seizures, psychomotor retardation, hypotonia, hyperreflexia, and lethargy. Urine amino acids may show elevated GABA, homocarnosine, and beta-alanine. Differential diagnosis includes succinic semialdehyde dehydrogenase deficiency (SSADHD), cerebral gigantism, globoid cell leukodystrophy, and Pelizaeus-Merzbacher disease. GABA-transaminase deficiency is diagnosed through accurate determination of elevated CSF GABA and beta-alanine, which can be done by liquid chromatography-electrospray-tandem mass spectrometry (01). Confirmation can be achieved by enzymatic activity or molecular analysis. MR spectroscopy with special editing for small molecules has been used as an alternative to CSF to make this diagnosis. As opposed to succinic semialdehyde dehydrogenase deficiency, which is diagnosed by elevated urinary γ-hydroxybutyrate (GHB), the GHB levels in GABA-transaminase deficiency are low.

Key points

• GABA-transaminase deficiency is inherited as an autosomal recessive disorder.

• This disorder is characterized by high levels of GABA in serum and CSF.

• Patients manifest with abnormal development and seizures.

• There are 18 confirmed, published cases of GABA-transaminase deficiency.

Historical note and terminology

GABA-transaminase deficiency was initially reported in 2 of 4 siblings in a single Flemish family (16). Only the female, who died at 2 years of age, was confirmed enzymatically. An older brother, who died previously at 1 year of age, had similar clinical symptomatology. A report and literature review published 10 cases, including the original family noted above (22).

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