TTC21B and Renal insufficiency: For example, monitoring renal function is likely to be more important for patients carrying a pathogenic variant in IFT140, TTC21B, or WDR19 than for patients who carry DYNC2H1 or IFT80 variants, as the latter two are primarily associated with a skeletal phenotype and IFT140, TTC21B, and WDR19 are associated with a skeletal phenotype accompanied by renal insufficiency and retinal degeneration [2, 10].