Risk Factors for Severe Renal Disease in Bardet–Biedl Syndrome

Bardet-Biedl syndrome is a rare autosomal recessive, multisystem disease characterized by retinal dystrophy, renal malformation, obesity, intellectual disability, polydactyly, and hypogonadism. Nineteen disease-causing genes ( BBS1-19 ) have been identified, of which mutations in BBS1 are most common in North America and Europe. A hallmark of the disease, renal malformation is heterogeneous and is a cause of morbidity and mortality through the development of CKD. We studied the prevalence and severity of CKD in 350 patients with Bardet-Biedl syndrome-related renal disease attending the United Kingdom national Bardet-Biedl syndrome clinics to further elucidate the phenotype and identify risk indicators of CKD. Overall, 31% of children and 42% of adults had CKD; 6% of children and 8% of adults had stage 4-5 CKD. In children, renal disease was often detected within the first year of life. Analysis of the most commonly mutated disease-associated genes revealed that, compared with two truncating mutations, two missense mutations associated with less severe CKD in adults. Moreover, compared with mutations in BBS10 , mutations in BBS1 associated with less severe CKD or lack of CKD in adults. Finally, 51% of patients with available ultrasounds had structural renal abnormalities, and 35% of adults were hypertensive. The presence of structural abnormalities or antihypertensive medication also correlated statistically with stage 3b-5 CKD. This study describes the largest reported cohort of patients with renal disease in Bardet-Biedl syndrome and identifies risk factors to be considered in genetic counseling.