A family study of Tourette syndrome in Japan

Although the mode of inheritance remains in doubt, twin and family studies conducted mostly in the United States and western Europe suggest that genetic factors play an important role in the transmission and expression of Tourette syndrome (TS). In an effort to evaluate population-based genetic differences, we generated risk estimates for first-degree relatives of TS probands in Japan using methods similar to those utilized in recent Western studies. The subjects were 52 TS probands seen at an outpatient clinic of Tokyo University Hospital and their 165 first-degree relatives. All probands and one or more first-degree relatives in each family were interviewed concerning the presence of tic and obsessive-compulsive symptoms by expert clinicians. The age-corrected rates of TS, chronic motor tics, obsessive-compulsive disorder, and subclinical obsessive-compulsive symptoms in the first-degree relatives were 2.0%, 12.0%, 1.6%, and 7.0%, respectively. Rates of TS and related disorders in Japan appear to be much lower than those in recent Western family studies. If replicated, these data suggest that there may be differences in the nature and frequency of vulnerable alleles for TS and related disorders in the Japanese compared to European populations.