Case report: Characterization of a patient with novel biallelic variants in GTF3C3 and comprehensive review of previously reported cases.

Biallelic variants in GTF3C3 have been recently associated with an autosomal recessive form of syndromic intellectual disability, with only 16 patients reported to date. Using whole exome sequencing, we identified previously unreported biallelic GTF3C3 variants in a new patient, who also represents the oldest reported individual so far. We detail the genotype and phenotype of this case and provide a comprehensive review of all published patients to better define the clinical features and their frequency. The most consistent manifestations across the cohort include global developmental delay, intellectual disability, epilepsy, central nervous system malformations, and additional neurological abnormalities. This case, together with the literature review, further delineates the phenotype associated with GTF3C3.