INTRODUCTION

Gamma aminobutyric acid transaminase(GABA-T) deficiency is an extremely rare disorder caused due to an inborn error in GABA degradation. It is diagnosed on the basis of raised GABA levels in CSF, serum, urine and genetic testing which shows mutations in the aminobutyrate aminotransferase(ABAT) gene, which is responsible for the catabolism of GABA. Here we report two siblings with genetically proven GABA–T deficiency, probably first ones to be reported surviving into adulthood in comparison to previously published case series.

CASE REPORT

The patients are two male siblings from India, now 21 and 15 years, born of third degree consanguineous union to Indian-Muslim parents. The index case is the younger sibling with onset of symptoms & regression from 2 years of age. His clinical course is characterized by marked developmental delay, intractable seizures, difficult fluctuant behavior and involuntary movements. General physical examination showed no dysmorphic features while neurological examination revealed pyramidal signs with movement disorders. Early Electroencephalography(EEG) showed hypsarrhythmia which then evolved to Lennox-Gastaut syndrome(LGS). Neuroimaging done on three occasions have demonstrated mild progressive cerebral atrophy. All work up was negative other than Next Generation Sequencing (NGS) which revealed a homozygous missense variation in exon 16 of ABAT gene in both siblings; parents being carriers.

CONCLUSION

1)    Contradictory to earlier reports, GABA-T deficiency can present with a varied phenotypic- genotypic spectrum.

2)    Role of correct anti-epileptic drugs in refractory epilepsy with this condition remains to be elucidated.