<unk>  is a pleiotropic disorder with variable expressivity and a wide range of clinical variability observed both within and between families. The most common clinical features are rod–cone dystrophy, with childhood-onset night-blindness followed by increasing visual loss; postaxial polydactyly; truncal obesity that manifests during infancy and remains problematic throughout adulthood; varying degrees of learning disabilities; male hypogenitalism and complex female genitourinary malformations; and renal dysfunction, a major cause of morbidity and mortality. There is a wide range of secondary features that are sometimes associated with BBS including * Strabismus, cataracts, astigmatism, pigmentary retinopathy, poor visual acuity, low vision, and/or blindness caused by an impaired photoreceptor transport mechanism in the retina. * "Brachydactyly, syndactyly of both the hands and feet is common, as is partial syndactyl (most usually between the second and third toes)" * Polyuria/polydipsia (nephrogenic diabetes insipidus) * Ataxia/poor coordination/imbalance * Mild hypertonia (especially lower limbs) * Diabetes mellitus * Hepatic involvement * Anosmia * Auditory deficiencies * Hirschsprung disease and subsequent bowel obstruction has been described. * Hypertrophy of interventricular septum and left ventricle and dilated cardiomyopathy. * Hypogonadism, kidney failure, urogenital sinuses, ectopic urethra, uterus duplex, septate vagina, and hypoplasia of the uterus, ovaries, and fallopian tubes * Speech disorder/delay * Developmental delay, especially of fine and gross motor skills Relation to other rare genetic disorders Findings in genetic research published in 2006 have suggested that a large number of genetic disorders, both genetic<unk> s and genetic diseases, that were not previously identified in the medical literature as related, may be, in fact, highly related in the genetypical root cause of the widely varying, phenotypically observed disorders. BBS is one such<unk>  that has now been identified to be caused by defects in the cellular ciliary structure. Thus, BBS is a ciliopathy. Other known ciliopathies include primary ciliary dyskinesia, polycystic kidney and liver disease, nephronophthisis, Alström<unk> , Meckel–Gruber<unk>  and some forms of retinal degeneration.
Bardet–Biedl syndrome
Prader–Willi syndrome
Schinzel–Giedion syndrome
Beckwith–Wiedemann syndrome
Langer–Giedion syndrome
Wiedemann–Steiner syndrome
Smith–Magenis syndrome
Wiedemann–Rautenstrauch syndrome