Phenotyping GABA transaminase deficiency: a case description and literature review

• Autor(a) principal: Louro, P
• Data de Publicação: 2016
• Outros Autores: Ramos, L, Robalo, C, Cancelinha, C, Dinis, A, Veiga, R, Pina, R, Rebelo, O, Pop, A, Diogo, L, Salomons, GS, Garcia, P
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.4/2050
• topic: Erros Inatos do Metabolismo; 4-Aminobutirato Transaminase/deficiência; 4-Aminobutirato Transaminase/genética

Gamma-aminobutyric acid transaminase (GABA-T) deficiency is an autosomal recessive disorder reported in only three unrelated families. It is caused by mutations in the ABAT gene, which encodes 4-aminobutyrate transaminase, an enzyme of GABA catabolism and mitochondrial nucleoside salvage. We report the case of a boy, deceased at 12 months of age, with early-onset epileptic encephalopathy, severe psychomotor retardation, hypotonia, lower-limb hyporeflexia, central hypoventilation, and rapid increase in weight and, to a lesser rate, length and head circumference. He presented signs of premature pubarche, thermal instability, and water-electrolyte imbalance. Serum total testosterone was elevated (43.3 ng/dl; normal range <16), as well as serum growth hormone (7.7 ng/ml; normal range <1). Brain magnetic resonance imaging (MRI) showed decreased myelination and generalized brain atrophy, later confirmed by post-mortem examination. ABAT gene sequencing was performed post-mortem, identifying a homozygous variant c.888G > T (p.Gln296His),not previously described. In vitro analysis concluded that this variant is pathogenic. The clinical features of this patient are similar to those reported so far in GABA-T deficiency. However, distinct mutations may have a different effect on enzymatic activity, which potentially could lead to a variable clinical outcome. Clinical investigation aiming for a diagnosis should not end with the patient's death, as it may allow a more precise genetic counselling for the family.