Chromosomal Abnormalities and Bipolar Affective Disorder: Velo-Cardio-Facial Syndrome

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Medscape Psychiatry & Mental Health eJournal. 1997;2(4) 

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Chromosomal Abnormalities Associated With Bipolar Disorder

Craddock and Owen's[24] review of the literature found reports of 7 cytogenetic surveys of samples of psychiatric patients, which included subjects with mood disorders, and 22 case reports of chromosome abnormalities co-occurring with affective disorder. However, no consistent associations between a cytogenetic abnormality and bipolar disorder emerged from these surveys. The investigators concluded that there are very few reports of cytogenetic abnormalities associated with mood disorders. Since significant chromosomal abnormalities such as aneuploidy, translocations, deletions, or other structural aberrations occur in approximately 1 in 200 live births,[25] one would expect co-occurrence of mood disorders and a significant chromosomal abnormality once in every 200 bipolar disorder patients merely by chance association.

If bipolar disorder and a genetically transmitted disease (or trait) determined by a single gene are associated within families, there could be a number of possible explanations:

  • The 2 distinct disorders are different manifestations of the same genetic defect, known as pleiotropy,

  • Both conditions are caused by genes that are in such close proximity that linkage is displayed, or

  • The two conditions are caused by a contiguous deletion syndrome--that is, the 2 genes are both deleted from the chromosome.

If bipolar disorder is found to be strongly associated with a specific chromosomal abnormality, the location of the altered genetic material can then be analyzed through linkage analysis. Two gene conditions--Darier's disease and VCFS--are caused by known chromosomal abnormalities and have been found to be associated with bipolar disorder (Table I).

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