Eur J Med Genet 2018 Dec 27;61(12):759-764. Epub 2018 Sep 27.
Laboratory of Embryology and Genetics of Congenital Malformations, INSERM UMR1163, Imagine Institute, Paris, France; Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, Paris, France; Pediatric Neurology, APHP- Necker Enfants Malades University Hospital, Paris, France; Reference Center "Déficiences Intellectuelles de Causes Rares", APHP- Necker Enfantes Malades University Hospital, Paris, France. Electronic address:
The advent of next generation sequencing has improved gene discovery in neurodevelopmental disorders. A greater understanding of the genetic basis of these disorders has expanded the spectrum of pathogenic genes, thus enhancing diagnosis and therapeutic management. Genetic overlap between distinct neurodevelopmental disorders has also been revealed, which can make determining a strict genotype-phenotype correlation more difficult. Intellectual disability and cortical malformations are two neurodevelopmental disorders particularly confronted by this difficulty. Indeed, for a given pathogenic gene, intellectual disability can be associated, or not, with cortical malformations. Here, we report for the first time, two individuals with the same de novo mutation in TBR1, leading to a frameshift starting at codon Thr532, and resulting in a premature stop codon 143 amino acids downstream (c.1588_1594dup, p.(Thr532Argfs*144)). These individuals presented with a developmental encephalopathy characterized by frontal pachygyria and severe intellectual disability. Remarkably, 11 TBR1 gene mutations were previously reported in intellectual disability and autism spectrum disorders. Our study supports the observation that TBR1-related disorders range from intellectual disability to frontal pachygyria. We also highlight the need for first-line, good quality neuroimaging for patients with intellectual disability.