Objective: To investigate the frequency and pattern of bilineal transmissio
n 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 indivi
duals), and 2) normal control subjects randomly selected from public school
s (20 family sets; 60 individuals). All patients with TS, normal control su
bjects, and their parents were evaluated for evidence of TS and associated
features. Structured interviews and detailed questionnaires designed to ass
ess ties, obsessive-compulsive behavior (OCB), and attention deficit disord
er (ADD) were administered to all people in both groups. Results: In additi
on 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 o
ne 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 addit
ional 13 (25.5%) TS families manifested evidence of bilineal transmission (
both parents affected). More fathers than mothers of patients with TS had t
ies (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%) child
ren in the general school population had some evidence of TS. One of 40 par
ents 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 OC
B, Conclusions: This study found evidence for bilineal transmission in one
fourth of TS families. Features of the TS spectrum were rare in normal cont
rol families. Evidence of ties, OCB, and ADD should be investigated in both
parents of patients with TS.