Dual rare genetic variants: case report of a child with SBIDDS syndrome and citrullinemia type 1

The arginine methyltransferase 7 (PRMT7) gene plays a role in signal transduction and protein interactions and negatively regulates neuronal differentiation. Pathogenic variants of PRMT7 cause SBIDDS syndrome (Short stature, brachydactyly, intellectual developmental disability, and seizures). PRMT7 has been shown to interact with the argininosuccinate synthetase (ASS1) gene; biallelic pathogenic variants of ASS1 are associated with citrullinemia type 1. We report a patient with biallelic variants for SBIDDS syndrome and citrullinemia type 1. The child exhibits severe intellectual disability, microcephaly, dysmorphisms, and seizures, consistent with the characteristics of these conditions. Exome sequencing identified variants c.1575 +1 G > A and c.232 dupT;p.Leu78Phefs*24 (NM_019023) in compound heterozygosity in the PRMT7 gene and variants c.1168G > A;p.Gly390Arg and c.-5-10C > G in exon 3 of the ASS1 gene (previously also identified in neonatal metabolic screening). The patient also has Wolf-Parkinson-White syndrome (WPW), behavioral issues, and brain morphological abnormalities, features that are poorly described in prior studies. It is not yet clear whether the clinical severity observed in this patient could also be partially due to interactions between these variants, as such interactions are not well-documented in the literature. Further research is necessary to elucidate the interplay between these two genes.