Identification of a Novel TRIT1 Mutation in a Consanguineous Iranian-Azeri-Turkish Family With Global Developmental Delay.

Global developmental delay (GDD) and intellectual disability (ID) affect up to 3% of the paediatric population, with a multifactorial aetiology that complicates genetic identification. To date, over 400 genes have been implicated in GDD. Here, we report a novel homozygous splice acceptor variant, NC_000001.11(NM_017646.6):c.1235-3C>G, in the TRIT1 gene, classified as 'likely pathogenic' through bioinformatics analysis. The proband, a 5-year-old male from a consanguineous family, presented with severe GDD, microcephaly, progressive spasticity, contractures, dysmorphic features (low-set ears, high-arched palate, simian creases and hypospadias), and refractory seizures (focal motor clonic, generalized myoclonic, and tonic) since 6 months of age. Brain MRI revealed nonspecific atrophy, while metabolic, laboratory and electrophysiological evaluations were unremarkable. To further assess the variant's frequency, we screened 430 healthy individuals from the same ethnic group and found no occurrences of the variant. Notably, this variant has not been documented in any published population databases, including gnomAD, the 1000 Genomes Project, Genome Asia, GME Variome and Iranome, despite coverage of the locus in these databases. Taken together, these findings strongly support the potential pathogenicity of the variant. In addition, the prenatal diagnosis results from the subsequent pregnancy in this family showed that the embryo was heterozygous for the mutation. The baby was born, and follow-up studies indicated that she was healthy, with no clinical manifestations observed in her affected brother. This further supports the classification of the variant as 'likely pathogenic.' This study expands the phenotypic spectrum of TRIT1-related disorders.