DISTRIBUTION OF THE B33 CTG REPEAT POLYMORPHISM IN A SUBTYPE OF SCHIZOPHRENIA

Clinical evidence for a dominant mode of inheritance and anticipation in periodic catatonia, a distinct subtype of schizophrenia, suggests t hat trinucleotide repeat expansions may be involved in the aetiology o f this disorder. Since genes with triplet repeats are putative can dil ates for causing schizophrenia, we have analysed the polymorphic B33 C TG repeal locus on chromosome 3 in 45 patients with periodic catatonia and 43 control subjects. The B33 CTG repeat locus was highly polymorp hic, but all alleles in both the patient and control groups had repeat lengths within the normal range. We conclude that susceptibility to p eriodic catatonia is not influenced by variation at the B33 CTG repeat locus. Nevertheless, that periodic catatonia displays dominant inheri tance and anticipation, characteristic of genetic disorders involving trinucleotide repeats, justifies further screening for triplet repeal expansions in this illness.