This study is based on the study of the natural history of a rare disorder: the Bardet-Biedl syndrome (BBS) (which is associated with retinitis pigmentosa, polydactyly, cognitive impairment, obesity, and kidney failure). The clinical, biological, and radiological features of adult patients are studied. In parallel, a molecular study is performed on the known genes to date (8 genes from BBS1 to BBS8) and to identify new genes involved. The parts of the study are combined in a phenotype-genotype correlation study.