RESUMO
OBJECTIVES: Much interest has recently been focused on the possibility of the involvement of unstable DNA in the etiology of schizophrenia following several publications that reported increases in frequency of large CAG repeats in affected individuals. Tardive dyskinesia(TD), an involuntary movement disorder following pharmacological treatment of schizophrenia, shares a great deal of common clinical and biological features with Huntington's disease, a representative movement disorder with CAG repeat expansions. The authors studied for a possible CAG repeat expansions in patients with schizophrenia and TD. METHODS: TD was diagnosed by the Abnormal Involuntary Movement Scale. Using repeat expansion detection(RED), a method in which a thermostable ligase is used to detect repeat expansions directly from genomic DNA, subjects with schizophrenia with/without TD(n=79/n=75) and normal controls (n=72) were studied for the presence of the CAG repeat expansions were analyzed. RESULTS: No significant size differences were detected in the(CTG)17 ligation products between schizophrenic cases and controls using RED(X(2)=2.907, df=2, p=0.234). CONCLUSIONS: This finding does not support the hypothesis that CAG repeat expansions contributes to the susceptibility for schizophrenia and TD.