Anticipation is not associated with CAG repeat expansion in parent-offspring pairs of patients affected with schizophrenia.

With the rationale that a disease that presents with anticipation could be associated with expansion of trinucleotide repeats, we selected parent-offspring pairs of schizophrenia patients with earlier age at onset in the filial generation to measure the expansion of CAG repeats using the repeat expansion detection (RED) method. Intergenerational comparisons were made for age at onset, length of CAG repeats, and clinical variables. Although the patients from the filial generation became affected 13 years earlier than the parents (P < 0.0005), we did not find larger CAG repeats in the offspring. No association was found between size of CAG repeat and age at onset or with any other clinical variable. Overall, the frequency of patients with CAG repeats longer than 40 was 32%, which was similar to that observed in control subjects (27%). It is particularly noteworthy that in 86% of the pairs, the mother was the affected parent. In this Spanish sample with parent-offspring pairs presenting schizophrenia with clinical anticipation and apparent female bias of transmission, neither the phenomenon of anticipation nor disease status was associated with the expansion of CAG repeats.