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Severe infantile epileptic encephalopathy due to mutations in PLCB 1 : expansion of the genotypic and phenotypic disease spectrum
Author(s) -
Ngoh Adeline,
McTague Amy,
Wentzensen Ingrid M,
Meyer Esther,
Applegate Carolyn,
Kossoff Eric H,
Batista Denise A,
Wang Tao,
Kurian Manju A
Publication year - 2014
Publication title -
developmental medicine and child neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.658
H-Index - 143
eISSN - 1469-8749
pISSN - 0012-1622
DOI - 10.1111/dmcn.12450
Subject(s) - sanger sequencing , epilepsy , genetics , medicine , pediatrics , global developmental delay , genotype , genetic testing , compound heterozygosity , mutation , phenotype , biology , gene , psychiatry
Homozygous deletions of chromosome 20p12.3, disrupting the promoter region and first three coding exons of the phospholipase C β 1 gene ( PLCB 1 ), have previously been described in two reports of early infantile epileptic encephalopathy ( EIEE ). Both children were born to consanguineous parents, one presented with infantile spasms, the other with migrating partial seizures of infancy. We describe an infant presenting with severe intractable epilepsy (without a specific EIEE electroclinical syndrome diagnosis) and neurodevelopmental delay associated with compound heterozygous mutations in PLCB 1 . A case note review and molecular genetic investigations were performed for a child, approximately 10 months of age, admitted to J ohns H opkins U niversity H ospital for developmental delay and new‐onset seizures. The patient presented at 6 months of age with developmental delay, followed by the onset of intractable, focal, and generalized seizures associated with developmental regression from 10 months of age. Presently, at 2 years of age, the child has severe motor and cognitive delays. Diagnostic microarray revealed a heterozygous 476kb deletion of 20p12.3 (encompassing PLCB 1 ), which was also detected in the mother. The genomic breakpoints for the heterozygous deletion were determined. In order to investigate the presence of a second PLCB 1 mutation, direct Sanger sequencing of the coding region and flanking intronic regions was undertaken, revealing a novel heterozygous intron 1 splice site variant (c.99+1G>A) in both the index individual and the father. Advances in molecular genetic testing have greatly improved diagnostic rates in EIEE , and this report further confirms the important role of microarray investigation in this group of disorders. PLCB 1‐ EIEE is now reported in a number of different EIEE phenotypes and our report provides further evidence for phenotypic pleiotropy encountered in early infantile epilepsy syndromes.