GABA Transaminase (GT) deficiency
Incidence
This autosomal recessive disease has been reported in only one family (brother and sister) but recently two other patients have been detected.
Clinical Characteristics
It seems to be the most severe of the disorders of the GABA pathway. These siblings showed pronounced axial hypotonia and generalized convulsions. From birth they had severe feeding problems that needed nasogastric tube feeding. The patients were characterized by lethargy and extremely pronounced psychomotor retardation. The patients had frequent vomiting and anorexia. CNS symptoms included seizures but mainly mental retardation with lethargy and axial hypotonia. Occasionally, hyperreflexia can be present in the neonatal period and early infancy. A paradoxical acceleration of the growth velocity was noted and found to be due to hypersecretion of growth hormone. A huge increase in free GABA was found in the CSF. Homocarnosine and beta-alanine were also increased but to a lesser degree. This was associated with a decreased GABA transaminase activity in liver and lymphocytes. Leukodystrophy of the type seen in aminoacidopathies such as PKU has been seen. No efficient treatment has been found for this disease which had a rapid fatal evolution in both children.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
EB-L, EB-W. There is decreased GABA transaminase activity in liver and lymphocytes. A huge increase in free GABA was found in the CSF. Homocarnosine and beta-alanine were also increased but to a lesser degree.