Ciliopathies are a large group of rare and severe genetic diseases caused by ciliary dysfunction, in which nearly all organs can be affected. In spite of being individually rare, they affect collectively up to one per 2000 people. Over the past two decades, more than 90 genes have been reported as mutated in ciliopathy patients. Most proteins encoded by these genes play key roles in the biogenesis or function of cilia, in which they define different functional subdomains. Genetic analyses of ciliopathies revealed a vast clinical variability and a broad genetic heterogeneity as: 1) mutations of the same disease-causing gene can result in distinct clinical entities and, conversely, 2) mutations in several independent genes can lead to similar clinical features, implying both phenotypic and genetic overlaps. The extent and severity of organ involvement may be correlated in part with the nature or location of the mutational event, the cell/tissue specific expression and effect of the mutated protein on cilia dysfunction.
Renal involvement is one of the most frequent manifestations in ciliopathies, and it leads to excessive morbidity and mortality. This includes renal cystic dysplasia (RCD), a kidney developmental defect, and nephronophthisis (NPHP), a chronic tubulointerstitial nephritis, both disorders representing frequent causes of end-stage renal disease (ESRD) during childhood to early adulthood. This makes ESRD a terminal endpoint of either isolated or syndromic ciliopathies, with, hitherto, no available curative treatment of chronic kidney disease whatsoever. The only bearable option is renal transplantation. As the average life-span of a functioning kidney transplant is about 10-15 years, it is urgent to identify therapeutic solutions that slow down progression of CKD in ciliopathies, and delay or avoid dialysis or transplantation. Today, the diagnosis of ciliopathies is first based on primary clinical manifestations, and then confirmed by gene mutation identification. However, even in patients with identified causative mutations, it is impossible to predict the severity of the disease, the risk of appearance (if not present at diagnosis), and/or the rate of progression of CKD. Thus, a crucial issue in the field of ciliopathies is to be able to perform early detection of at-risk patients prior to development of CKD as well as to predict disease progression rate.
