Cytogenetic findings in 250 schizophrenics: evidence confirming an excess of the X chromosome aneuploidies and pericentric inversion of chromosome 9.

Chromosomal abnormalities may be of help in identifying disease genes. To search for susceptibility loci for schizophrenia, we have performed chromosomal examinations by using the GTG banding technique for 250 schizophrenics. We found five cases with an aneuploidy of the X chromosome and ten cases with pericentric inversion of chromosome 9 [inv (9)]. These results confirmed an excess of the X chromosome aneuploidies in schizophrenia, indicating a possible involvement of the X chromosome in the pathogenesis of the illness. The observed incidence (4.0%) of inv (9) in our schizophrenic sample was significantly higher (p=0.013) than that reported in the general population in Japan (1.7%). Although inv (9) has been considered to be a normal variant, our observation implies a possible association between inv (9) and schizophrenia, suggesting that a susceptibility locus for the disease may be located at a breakpoint of the inversion on chromosome 9.