This study will evaluate patients with a rare inherited condition called Bardet-Biedl syndrome . The purpose of the study is to learn more about the genetics and clinical characteristics of this disorder. Patients may have the following problems: polydactyly (extra fingers and toes); retinal dystrophy (changes in the retina that may lead to vision problems, including blindness); obesity and diabetes (overweight and high blood sugar due to failure of body organs to respond to insulin); cognitive dysfunction (difficulties with learning and understanding); hypogenitalism (decreased functioning of the ovaries in women and the testes in men); kidney anomalies (changes in the structure or function of the kidneys); heart disease; and hepatic fibrosis (liver disease).