Trisomy 8 mosaicism 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.

Trisomy 8 mosaicism syndrome is a genetic disorder that can affect neurodevelopment and multiple organ systems. It is a chromosomal mosaicism disorder arising predominantly through postzygotic events, and non-mosaic trisomy 8 is generally not compatible with live birth. It is generally a sporadic condition arising de novo rather than an inherited disorder, so a relevant family history would be unexpected. A distinctive presentation may include the combination of a thick vermilion, deep-set eyes, prominent ears, and camptodactyly.

It can present with psychiatric features such as intellectual disability, learning difficulties, behavioural problems, and, rarely, psychosis. Psychiatric manifestations may become apparent or clinically significant during adolescence or adulthood; psychosis has been reported as a presenting feature in young adulthood.

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

  • Prominent forehead

  • Midface retrusion

  • Micrognathia

  • Widely spaced eyes

  • Broad nasal bridge

  • Thick vermilion

  • Single transverse palmar crease

Other characteristic features include developmental delay, hypotonia, seizures, and structural brain abnormalities such as agenesis of the corpus callosum.

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

  • Cardiovascular: congenital heart disease, including septal defects and other structural cardiac abnormalities.

  • Respiratory: respiratory abnormalities may occur, particularly in individuals with associated structural anomalies.

  • Renal/electrolytes: renal and urinary tract abnormalities, including hydronephrosis, may occur.

  • Endocrine: hypothyroidism may occur.

  • Musculoskeletal: vertebral and other skeletal abnormalities, absent or hypoplastic patellae, camptodactyly, joint contractures or progressive limitation of joint mobility, and other limb abnormalities.

  • Dermatologic: deep furrows or creases of the soles are particularly characteristic; pigmentary abnormalities may also occur.

Early diagnosis is important to identify potentially treatable medical contributors to psychiatric and cognitive presentations, recognize congenital cardiac, renal, neurologic, and musculoskeletal complications, guide appropriate surveillance, and enable timely treatment of psychiatric illness and other comorbidities.

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.