EP193: Co-occurring TCF12 and mosaic NALCN likely pathogenic variants: Case report of novel skeletal findings without craniosynostosis, neurologic dysfunction, and apnea

Abstract

We report a unique clinical case of an 18-month-old patient with skeletal dysplasia, neurologic dysfunction, and apneic events caused by a novel combination of genetic variants. Whole exome sequencing (WES) identified two likely pathogenic variants, with one being mosaic, which is distinctive given the difficult nature of WES technology. The first variant was a de novo, heterozygous missense variant (c.1882T>C; p.Cys628Arg) in exon 19 of the TCF12 gene. The second is a mosaic single amino acid deletion (c.4299_4301delCAT; p.Ile1434del) in exon 38 of the NALCN gene, which was detected in 30% of the sequencing reads.