👤 Maria Piccione

Mutations in GABRB3 have been identified in subjects with different types of epilepsy and epileptic syndromes, including West syndrome (WS), Dravet syndrome (DS), Lennox-Gastaut syndrome (LGS), myoclonic-atonic epilepsy (MAE), and others. We herewith report on a girl affected by DS, who has been followed from infancy to the current age of 18 years. Next-generation sequencing (NGS)-based genetic testing for multigene analysis of neurodevelopmental disorders identified two likely de novo pathogenic mutations, a missense variant in GABRB3 gene (c.842 C>T; p.Thr281IIe) and a nonsense variant found in BBS4 gene (c.883 C>T; p.Arg295Ter). A likely relationship between the novel GABRB3 gene variant and the clinical manifestations presented by the girl is proposed. Previously, one case of DS and two of DS-like linked with GABRB3 mutations have been reported. To the best of our knowledge, this is the first report of DS associated with this novel variant. A literature review of clinical cases with various types of epileptic encephalopathies (EEs) related to GABRB3 mutations is reported. Show less

The 17q21.31 deletion syndrome phenotype can be caused by either chromosome deletions or point mutations in the KANSL1 gene. To date, about 60 subjects with chromosome deletion and 4 subjects with point mutation in KANSL1 have been reported. Prevalence of chromosome deletions compared with point mutations, genotype-phenotype correlations and phenotypic variability have yet to be fully clarified. We report genotype-phenotype correlations in 27 novel subjects with 17q21.31 deletion and in 5 subjects with KANSL1 point mutation, 3 of whom were not previously reported. The prevalence of chromosome deletion and KANSL1 mutation was 83% and 17%, respectively. All patients had similar clinical features, with the exception of macrocephaly, which was detected in 24% of patients with the deletion and 60% of those with the point mutation, and congenital heart disease, which was limited to 35% of patients with the deletion. A remarkable phenotypic variability was observed in both categories, mainly with respect to the severity of ID. Cognitive function was within normal parameters in one patient in each group. Craniosynostosis, subependymal heterotopia and optic nerve hypoplasia represent new component manifestations. In KANSL1 haploinsufficiency syndrome, chromosome deletions are greatly prevalent compared with KANSL1 mutations. The latter are sufficient in causing the full clinical phenotype. The degree of intellectual disability (ID) appears to be milder than expected in a considerable number of subjects with either chromosome deletion or KANSL1 mutation. Striking clinical criteria for enrolling patients into KANSL1 analysis include speech delay, distinctive facial dysmorphism, macrocephaly and friendly behaviour. Show less