Novel multi-allelic variants, two BBS2 and one PKD1 variant, of renal ciliopathies: A case report and literature review

Background: Bardet-Biedl syndrome (BBS) and autosomal dominant polycystic kidney disease (ADPKD) are renal ciliopathies. BBS has 22 pathogenic genes, and ADPKD is mainly caused by PKD1 and PKD2 variants.Cases with tri-allelic variants of BBS and PKD1 are rare. Case presentation: The proband was an 11-year-old Chinese male with cysts in both kidneys, blurred vision, hyperopia, and short fingers and toes. The patient underwent a kidney transplant due to rapid deterioration of renal failure. During follow-up, a smaller field of vision, a slow increase in height, and a weight gain were observed. In addition, renal function and anemia were improved. High-throughput sequencing analysis showed two heterozygous variants in BBS2 (c.563delT (p.I188Tfs*13) inherited from the father and c.534+1G > t (splicing) from the mother) and one heterozygous variant in PKD1 (c.6223C > T (p.R2075C)) inherited from the mother. Conclusion: This paper reported a ciliopathy patient with multi-allelic variants (two BBS2 variants and one PKD1 variant) that may lead to early symptoms and more rapid progression. An early genetic diagnosis may contribute to predicting disease progression and guiding management and follow-up.