Report of the committee on the genetic constitution of chromosome 1

Type I bipolar disorder associated with a fragile site on chromosome 1

The objective of this paper is to study the association between chromosomal fragile sites and type I bipolar disorder. This case-control study compares bipolar patients with normal controls. Ten cases of type I bipolar disorder diagnosed according to DSM-III-R criteria and the Composite International Diagnostic Interview (CIDI) were selected from the Escola Paulista affective disorders outpatient clinic and 10 healthy controls (CIDI negative for psychiatric diagnoses) matched for sex and age were drawn from the otorhinolaryngologic outpatient clinic of the same hospital. The cytogenetic analysis was carried out with blood lymphocytes, which were cultured in a folic acid-free medium. A total of 100 mitoses per subject were blindly analyzed to the psychiatric diagnostic assignment, and fragile sites were identified according to a minimum expected frequency of events per band in conformity with a Poisson distribution. A higher frequency of chromosomal lesions for cases than controls was found for the following bands: 1q32, 5q31, and 11q23, the 1q32 being considered a fragile site. Although no evident neuropsychiatric etiological component has been mapped to the 1q32 region so far, this finding may lead to further investigation of a possible linkage between genetic markers of this region and bipolar disorder.