Defects in BBS1 cause Bardet-Biedl syndrome 1 (BBS1) [MIM: 209900], an autosomal recessive and genetically heterogeneous ciliopathy characterized by retinitis pigmentosa, obesity, kidney dysfunction, polydactyly, behavioral dysfunction, and hypogonadism. This evidence concerns the gene BBS1 and obesity due to melanocortin 4 receptor deficiency.