De novo nonsense variant in ASXL3 in a Chinese girl causing Bainbridge-Ropers syndrome: A case report and review of literature

Background: Bainbridge-Ropers syndrome (BRPS, OMIM #615485) was first identified in 2013 by Bainbridge et al. and is a neurodevelopment disorder characterized by failure to thrive, facial dysmorphism and severe developmental delay. BRPS is caused by heterozygous loss-of-function (LOF) variants in the additional sex combs-like 3 (ASXL3) gene. Due to the limited specific recognizable features and overlapping symptoms with Bohring-Opitz syndrome (BOS, OMIM #612990), clinical diagnosis of BRPS is challenging. Methods: In this study, a 2-year-8-month-old Chinese girl was referred for genetic evaluation of severe developmental delay. The reduced fetal movement was found during the antenatal period and bilateral varus deformity of feet was observed at birth. Whole-exome sequencing and Sanger sequencing were used to detect and confirm the variant. Results: A novel nonsense variant c.1063G>T (p.E355*) in the ASXL3 gene (NM_030632.3) was identified in the proband and the clinical symptoms were compatible with BRPS. The parents were physical and genetic normal and prenatal diagnosis was requested for her pregnant mother with a negative Sanger sequencing result. Conclusion: The study revealed a de novo LOF variant in the ASXL3 gene and expanded the mutation spectrum for this clinical condition. By performing a literature review, we summarized genetic results and the clinical phenotypes of all BPRSs reported so far. More cases study may help to elucidate the function of the ASXL3 gene may be critical to understand the genetic aetiology of this syndrome and assist in accurate genetic counselling, informed decision making and prenatal diagnosis.