CYTOGENETIC ABNORMALITIES ON CHROMOSOME-18 ASSOCIATED WITH BIPOLAR AFFECTIVE-DISORDER OR SCHIZOPHRENIA

Background A few recent linkage studies have shown a possible locus fo r bipolar disorder on chromosome 18. Cytogenetic studies may assist in the further localisation of susceptibility loci on this chromosome. M ethod A search was made or abnormalities of chromosome 18 in two separ ate large cytogenetic databases. In Denmark detection of mental illnes s in subjects with chromosome abnormalities was done by cross-linking the two separate registers of psychiatric and chromosome disorders. In Scotland the Cytogenetic Registry of the MRC Human Genetics Unit unde rtakes long-term clinical follow-up of ail cases with chromosome abnor malities. Results Cross-linking the two Danish registers revealed a fa mily with the rare karyotype abnormality inv(18) (p11.3;q21.1) with on e inversion carrier who also suffered from bipolar disorder. in this f amily there were two other cases of bipolar disorder, but the karyotyp e of these cases could not be established. One family in Scotland show ed a case of schizophrenia in a carrier of inv(18) with the same break points as the Danish family Conclusions We suggest further studies of the 18p11.3 and 18q21.1 regions in order to identify genes involved in bipolar affective disorder and schizophrenia.