Non-Syndromic X Linked Intellectual Disability in Two Brothers with A Novel NLGN4X Gene Splicing Mutation (NC_018934.2: g. 1202C>A)

X-linked Intellectual Disability (XLID) is an extremely heterogeneous disorder for which many of the causative genes are still unknown. So far, more than one hundred genes of the X chromosome have been found to be altered in males manifesting intellectual disability (ID). NLGN4X is an XLID gene, which has been found, involved in autism and Asperger syndrome involving causative coding mutations. Up to now a few pathological mutations in the promoter and the 5' UTR have been identified. Here we report a non-syndromic X linked Intellectual disability in two brothers with a novel NLGN4X splicing mutation predicted to have a pathogenic effect by the activation of an exonic cryptic acceptor site, with presence of one or more cryptic branch point(s). This mutation g.1202C>A (Genbank accession number NC_018934.2) was identified through X exome sequencing. It was confirmed by Sanger sequencing. The mother was heterozygous with a skewed X inactivation pattern (100%). She is not affected. This variant was predicted to change the splicing process leading to potential alteration of the mRNA. This mutation segregates with the pathological phenotype in all the affected males. However, it was absent in the non-affected daughter, we suggest that it could be in favor of genotype- phenotype correlation. This study also confirms the efficiency of X exome sequencing for identifying specific genetic conditions not clinically suspected.