Co-segregation of variant NSUN2 Lue198Arg among Iranian family with intellectual disability: a case report

Abstract Background Intellectual disability is characterized by impairments in adaptive behavior and cognitive functioning manifested during the developmental period. Since disabilities are heterogeneous, variant analysis can help us confirm and accurately diagnose children with intellectual disabilities. Some papers reported that bi-allelic variants of the NSUN2 gene caused a group of neurological disorders, including non-syndromic autosomal recessive intellectual disability (NS-ARID), Dubowitz syndrome, and familial restrictive cardiomyopathy 1 (RCM1). We report on a consanguineous family with three siblings diagnosed with intellectual disability. Case presentation The 7-year-old female was referred to Ali-Asghar hospital, Zahedan, Iran, with clinical manifestations comprising moderate intellectual disability, ptosis, long face, and short stature. Chromosome banding, metabolic testing, and magnetic resonance imaging examinations revealed no abnormalities. Accordingly, other affected siblings born of the same parents were considered. Whole-exome sequencing (WES) was conducted on the sufferer to consider NS-ARID variants. Findings identified a variant with uncertain significance (NM_017755.6: c.593 T > G) in the NSUN2 gene in the proband. This variant was confirmed through Sanger sequencing of the affected and unaffected family members. Besides, the computational results showed that the L198R exchange could change the interaction between wild-type and other residues in the protein. The affected patients with NS-ARID had similar clinical characteristics and genetic abnormalities. Conclusion Taken together, we described the variant in three Iranian siblings; further expanding of the other variants involved in the disease will be evident by using high-throughput sequencing technologies.