GABA-transaminase deficiency

Phillip L Pearl MD (Dr. Pearl of Boston Children's Hospital and Harvard Medical School has no relevant financial relationships to disclose.)
Ryan Hodgeman BS (Mr. Hodgeman of Boston Children's Hospital and Harvard Medical School has no relevant financial relationships to disclose.)
K Michael Gibson PhD (Dr. Gibson of Washington State University College of Pharmacy has no relevant financial relationships to disclose.)
Tyler Reimschisel MD, editor. (Dr. Reimschisel of Vanderbilt University has received contracted research grants from Shire and Vtesse.)
Originally released March 21, 1994; last updated October 20, 2016; expires October 20, 2019

This article includes discussion of GABA-transaminase deficiency, 4-aminobutyric acid aminotransferase deficiency, GABA-T deficiency, gamma-aminobutyric acid aminotransferase deficiency, gamma-aminobutyric acid transaminase deficiency, gamma-aminobutyrate aminotransferase deficiency, gamma-aminobutyrate transaminase deficiency, and 4-Aminobutyrate:2-oxoglutarate aminotransferase deficiency. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

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, cerebral gigantism, globoid cell leukodystrophy, and Pelizaeus-Merzbacher disease. GABA-transaminase deficiency is diagnosed through accurate determination of elevated CSF GABA and beta-alanine, and confirmation is 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.

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 6 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 (Jaeken et al 1984). 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. One confirmed patient of 28 months from an unrelated family was reported in 2010 (Tsuji et al 2010). Three cases were reported in 2015, including one set of siblings (female, deceased at age 7 years; male, alive at 7 years) (Besse et al 2015) and an unrelated male diagnosed posthumously at 12 months (Louro et al. 2016).

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