A novel intronic variant in ROBO3 associated with horizontal gaze palsy with progressive scoliosis: case report and literature review.

Horizontal gaze palsy with progressive scoliosis (HGPPS) is a rare, autosomal recessive inherited disorder caused by mutations in ROBO3 gene. The clinical features of HGPPS include horizontal gaze palsy, progressive scoliosis, other oculomotor abnormalities such as strabismus and nystagmus. Whole-exome sequencing (WES) is used to diagnose rare Mendelian disorders, when routine standard tests have failed to make a formal pathological diagnosis. However, WES may identify variants of uncertain significance (VUS) that may add further ambiguity to the diagnosis. We report the case of a 4-year-old boy with horizontal gaze palsy, progressive scoliosis, microcephaly, and mild developmental delay. WES identified an intronic VUS in ROBO3 gene. We performed minigene splicing functional analysis to confirm the pathogenicity of this VUS. This report illustrates that WES data analysis with supportive functional analysis provides an effective approach to improve the diagnostic yield for unsolved clinical cases. This case also highlights the phenotypic heterogeneity in patients with HGPPS.