Bardet–Biedl syndrome

Page most recently updated 7 September 2026

This page focuses on the reported psychiatric associations, which may be the initial presenting manifestation, and on other clinical features that may assist the psychiatrist or primary care physician in identifying the underlying diagnosis, considered through the lenses of the diagnostic lenses framework.

Bardet–Biedl syndrome is a genetic disorder that can affect neurodevelopment, vision, endocrine function, and multiple organ systems. It typically occurs as an inherited autosomal recessive genetic condition, so absence of a relevant family history does not exclude the diagnosis. A distinctive presentation may include the combination of obesity, postaxial polydactyly, and rod-cone retinal dystrophy. Progressive visual impairment commonly begins in childhood and may lead to severe visual loss by early adulthood.

It can present with psychiatric features such as behavioural difficulties, anxiety, depression, and other mood or behavioural abnormalities. Psychiatric manifestations may become apparent or clinically significant during adolescence or adulthood; psychosis has been reported but appears to be rare.

From a morphologic lens perspective, features include (but are not limited to):

  • Brachydactyly

  • Polydactyly (can involve hands, feet, or both, and may be unilateral or bilateral)

Other characteristic features include developmental delay, intellectual disability or learning difficulties, speech abnormalities, poor coordination or ataxia, and seizures in some individuals. Hypogonadism and genitourinary abnormalities may also occur.

From a multisystemic lens perspective, clinical features in other body systems include (but are not limited to):

  • Cardiovascular: congenital heart disease and other cardiovascular abnormalities may occur.

  • Renal/electrolytes: structural renal abnormalities, hydronephrosis, vesicoureteral reflux, renal parenchymal disease, and chronic kidney disease may occur; renal disease is a major cause of morbidity and mortality.

  • Hepatobiliary: liver disease may occur, including metabolic dysfunction-associated steatotic liver disease (MASLD) (formerly called non-alcoholic fatty liver disease [NAFLD]), biliary abnormalities, and hepatic fibrosis.

  • Endocrine: hypogonadism with delayed or incomplete pubertal development and infertility may occur; obesity-related insulin resistance, metabolic syndrome, type 2 diabetes, and hypothyroidism may also occur.

  • Musculoskeletal: postaxial polydactyly, brachydactyly, syndactyly, and other skeletal abnormalities may occur.

Early diagnosis is important to recognize progressive visual impairment and facilitate timely ophthalmologic surveillance and low-vision support, identify and manage obesity and its metabolic complications, detect potentially serious renal disease early, recognize hypogonadism and other endocrine abnormalities, provide appropriate developmental, educational, and psychiatric support, and enable lifelong multisystemic surveillance to improve prognosis and quality of life.

Selected references and further reading — Morphologic lens

Jones KL, Jones MC, del Campo M. Smith's recognizable patterns of human malformation. 8th ed. Philadelphia: Elsevier; 2021.

Reardon W. The bedside dysmorphologist: a guide to identifying and assessing congenital malformations. 2nd ed. Oxford: Oxford University Press; 2016.

Allanson JE, Biesecker LG, Carey JC, Hennekam RCM. Elements of morphology: introduction. Am J Med Genet A. 2009;149A(1):2-5. doi:10.1002/ajmg.a.32601.

Hennekam RCM, Biesecker LG, Allanson JE, Hall JG, Opitz JM, Temple IK, Carey JC; Elements of Morphology Consortium. Elements of morphology: general terms for congenital anomalies. Am J Med Genet A. 2013;161A(11):2726-2733. doi:10.1002/ajmg.a.36249.

Selected references and further reading — Multisystemic lens

Cardinal RN, Bullmore ET. The diagnosis of psychosis. Cambridge: Cambridge University Press; 2011.

Sachdev PS, Keshavan MS, editors. Secondary schizophrenia. Cambridge: Cambridge University Press; 2010.

Levenson JL, editor. The American Psychiatric Association Publishing textbook of psychosomatic medicine and consultation-liaison psychiatry. 3rd ed. Washington (DC): American Psychiatric Association Publishing; 2019.

Stern TA, Beach SR, Smith FA, Freudenreich O, Vranceau AM, Fava M, editors. Massachusetts General Hospital handbook of general hospital psychiatry. 8th ed. Philadelphia: Elsevier; 2025.

Arciniegas DB, Yudofsky SC, Hales RE, editors. The American Psychiatric Association Publishing textbook of neuropsychiatry and clinical neurosciences. 6th ed. Washington (DC): American Psychiatric Association Publishing; 2018.

Agrawal N, Faruqui R, Bodani M, editors. Oxford textbook of neuropsychiatry. Oxford: Oxford University Press; 2020.

Boland R, Verduin M, editors. Kaplan and Sadock's comprehensive textbook of psychiatry. 11th ed. Philadelphia: Wolters Kluwer; 2024.

Loscalzo J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Jameson JL, editors. Harrison's principles of internal medicine. 22nd ed. New York: McGraw Hill; 2025.