Bilineal transmission in Tourette syndrome

Objective: To investigate the frequency and pattern of bilineal transmission in families of patients with Tourette syndrome (TS) compared with normal control subjects. Methods: The study population consisted of two groups: 1) consecutive patients with TS with both parents (51 family sets; 153 individuals), and 2) normal control subjects randomly selected from public schools (20 family sets; 60 individuals). All patients with TS, normal control subjects, and their parents were evaluated for evidence of TS and associated features. Structured interviews and detailed questionnaires designed to assess ties, obsessive-compulsive behavior (OCB), and attention deficit disorder (ADD) were administered to all people in both groups. Results: In addition to ties, 43 (84.3%) patients with TS had ADD, 33 (64.7%) had OCB, and 31 (60.8%) had both ADD and OCB. In 42 (82.4%) of the 51 patients, at least one parent exhibited features of TS; unilineal transmission (only one parent with ties, OCB, or ADD) was present in 29 (56.9%) TS families and an additional 13 (25.5%) TS families manifested evidence of bilineal transmission (both parents affected). More fathers than mothers of patients with TS had ties (31.4% versus 15.7%), whereas more mothers had OCB than did fathers (33.3% versus 15.7%). Features of ADD were equally distributed among fathers (35.3%) and mothers (33.3%) of patients with TS. Eight of 1,142 (0.7%) children in the general school population had some evidence of TS. One of 40 parents of the normal control subjects (2.5%) had symptoms of ADD, but none of the parents of normal control subjects manifested any features of TS or OCB, Conclusions: This study found evidence for bilineal transmission in one fourth of TS families. Features of the TS spectrum were rare in normal control families. Evidence of ties, OCB, and ADD should be investigated in both parents of patients with TS.