HERC1 mutations should be considered in differential diagnosis of severe intellectual disability and behavioural problems, particularly in patients testing negative for fragile X and KANSL1 mutations.
Here, using a whole-exome sequencing in a Moroccan consanguineous family, we show that a novel autosomal-recessive neurological condition characterized by megalencephaly, thick corpus callosum and severe intellectual disability is caused by a homozygous nonsense variant in the HERC1 gene.