Molecular and clinical descriptions of patients with GABAA receptor gene variants (GABRA1, GABRB2, GABRB3, GABRG2): A cohort study, review of literature, and genotype-phenotype correlation.

OBJECTIVE: γ-Aminobutyric acid (GABA)A -receptor subunit variants have recently been associated with neurodevelopmental disorders and/or epilepsy. The phenotype linked with each gene is becoming better known. Because of the common molecular structure and physiological role of these phenotypes, it seemed interesting to describe a putative phenotype associated with GABAA -receptor-related disorders as a whole and seek possible genotype-phenotype correlations. METHODS: We collected clinical, electrophysiological, therapeutic, and molecular data from patients with GABAA -receptor subunit variants (GABRA1, GABRB2, GABRB3, and GABRG2) through a national French collaboration using the EPIGENE network and compared these data to the one already described in the literature. RESULTS: We gathered the reported patients in three epileptic phenotypes: 15 patients with fever-related epilepsy (40%), 11 with early developmental epileptic encephalopathy (30%), 10 with generalized epilepsy spectrum (27%), and 1 patient without seizures (3%). We did not find a specific phenotype for any gene, but we showed that the location of variants on the transmembrane (TM) segment was associated with a more severe phenotype, irrespective of the GABAA -receptor subunit gene, whereas N-terminal variants seemed to be related to milder phenotypes. SIGNIFICANCE: GABAA -receptor subunit variants are associated with highly variable phenotypes despite their molecular and physiological proximity. None of the genes described here was associated with a specific phenotype. On the other hand, it appears that the location of the variant on the protein may be a marker of severity. Variant location may have important weight in the development of targeted therapeutics.

Real-life data comparing the efficacy of vigabatrin and oral steroids given sequentially or combined for infantile epileptic spasms syndrome.

AIMS: The prognosis of Infantile epileptic spasm syndrome (IESS), relates to the underlying etiology and delay in controlling epileptic spasms. Based on the spasm-free rate, a randomized controlled trial has demonstrated the superiority of combining oral steroids and vigabatrin over oral steroids alone but confirmation in real-life conditions is mandatory. METHODS: We compared two real-life IESS cohorts: a multicenter, retrospective cohort of 40 infants treated with vigabatrin followed by a sequential (ST) addition of steroids, and a prospective, single-center cohort of 58 infants treated with an immediate combination of vigabatrin and steroids (CT). RESULTS: The two cohorts were similar. When the rate of spasm-free infants in the two cohorts was compared on day 14, a significant difference was observed between the ST (27,5 %) and CT cohorts (64 %) (p < 0.0004). This difference remained significant on day 30, with 55 % spasm-free patients in the ST cohort compared to 76 % in the CT cohort (p = 0.03). After the infants had received both vigabatrin and steroids, without taking into account the time point after treatment initiation, no significant difference was observed in the spasm-free rate between the two cohorts (p = 0.38). INTERPRETATION: Real-life data confirm the interest of combination therapy as a first-line treatment for IESS.