Tic symptom profiles in subjects with Tourette Syndrome from two genetically isolated populations.

Background: Tourette Syndrome (TS) has a complex etiology and wide variability in phenotypic expression. Identifying underlying symptom patterns may be useful for etiological and outcome studies of TS.
Methods: Lifetime tic and related symptom data were collected between 1996 and 2001 in 121 TS subjects from the Central Valley of Costa Rica and 133 TS subjects from the Ashkenazi Jewish (AS) population in the US. Subjects were grouped by tic symptoms using an agglomerative hierarchical cluster analysis. Cluster membership was tested for association with available ancillary information (age of onset, tic severity, comorbid disorders, medication treatment and family history).
Results: Cluster analysis identified two distinct groups in each sample, those with predominantly simple tics (cluster 1), and those with multiple complex tics (cluster 2). Membership in cluster 2 was correlated with increased tic severity, global impairment, medication treatment, and presence of comorbid obsessive-compulsive symptoms in both samples, and with family history of tics, lower verbal IQ, earlier age of onset, and comorbid obsessive-compulsive disorder and attention-deficit/hyperactivity disorder in the AS sample.
Conclusions: This study provides evidence for consistent and reproducible symptom profiles in two independent TS study samples. These findings have implications for etiological studies of TS.