Deciphering a Novel TTI2 Mutation in a Saudi Proband with IDDAR39: A Clinical and Genetic Study

Background: Intellectual Developmental Disorder, Autosomal Recessive 39 (IDDAR39) is a rare inherited condition caused by mutated TTI2 gene. The condition is characterized by intellectual disability and developmental delays, among other clinical features. Methods: We conducted a genetic study in a Saudi proband (II-1) with intellectual disability (ID), developmental delay, mild microcephaly, short stature, and skeletal abnormalities. To identify potential disease-causing variant, whole-exome sequencing (WES) and Sanger-sequencing was utilized. Results: WES analysis identified a bialelic TTI2-missense variant [c.1309T>G; p.(Cys437Gly)] in the proband (II-1). Disease causing variants in TTI2 have been previously associated with IIDAR39. The clinical features of the proband were consistent with the phenotypic presentation observed in other cases of IDDAR39. Conclusion: The TTI2-novel variant identified in the present study is likely responsible for the clinical manifestations observed in the proband. This finding supports the critical role of TTI2 in neurodevelopmental processes in humans.