Chromosome X Aneuploidy in Brazilian Schizophrenic Patients

The identification of cytogenetic abnormalities in schizophrenic patients may provide clues to the genes involved in this disease. For this reason, a chromosomal analysis of samples from 62 schizophrenics and 70 controls was performed with trypsin-Giemsa banding and fluorescence in situ hybridization of the X chromosome. A clonal pericentric inversion on chromosome 9 was detected in one male patient, and we also discovered mosaicism associated with X chromosome aneuploidy in female patients, primarily detected in schizophrenic and normal female controls over 40 years old. When compared with age- matched female controls, the frequency of X chromosome loss was not significantly different between schizophrenics and controls, except for the 40- to 49-year-old age group. Our findings suggest that the X chromosome loss seen in schizophrenic patients is inherent to the normal cellular aging process. However, our data also suggest that X chromosome gain may be correlated with schizophrenia in this Brazilian population. Schizophrenia is a common psychiatric disease with a genetic basis. However, to date, specific mutations associated with the disorder have not been identified. Current views on the genetics of schizophrenia are mainly based on a large set of linkage and cytogenetic studies suggesting that almost all human chromosomes may be involved in schizophrenia pathogenesis (1). In addition to some cases that show specific chromosomal translocations and deletions related to psychoses (2-5), sex chromosome anomalies (6-9) and pericentric inversions of chromosome 9 (inv(9)) (9-11) have also been reported in schizophrenic patients. In the present study, we report the chromosomal analysis of peripheral blood lymphocytes isolated from 62 schizophrenic patients and 70 controls, as well as an assessment of the relationship between the abnormalities found and disease subtype, gender, age at disease onset and family history. To evaluate the incidence of X chromosome mosaicism in the control group, sex and age-matched Brazilian controls were also studied. Although several studies have reported the systematic cytogenetic screening of schizophrenic individuals, few have performed fluorescence in situ hybridization (FISH) analysis. Furthermore, to our knowledge, this is the first study to evaluate chromosomal alterations in Brazilian schizophrenic patients.