Bilineal transmission and phenotypic variation of Tourette's disorder in a large pedigree.
OBJECTIVE
Variability in the clinical phenotype of Tourette's disorder (TD) was assessed in a single large family, with a focus on the influence of bilineal transmission.


METHODS
Tics, obsessive-compulsive symptoms, and attention-deficit symptoms were evaluated through interview and standardized checklists for 175 descendants and 16 spouses who married into a single four-generation pedigree.


RESULTS
Some form of tic disorder was diagnosed in 67% of descendants and 44% of married-in spouses. TD was found in 36% of descendants and in 31% of married-in spouses. Impairment was minimal in most cases, but age at onset and location and number of tics were typical of TD described in clinic samples. Obsessive-compulsive symptoms were found in 38% of descendants and 62% of those with current TD, but obsessive-compulsive disorder was found in only four individuals. Attention-deficit hyperactivity disorder occurred in 25% of children. Multivariate analysis indicated that offspring of two parents with tic disorders manifested significantly more lifetime tics, more severe categories of tic disorders, and an earlier age at onset for TD compared with offspring of one or no affected parents.


CONCLUSIONS
TD in this family is most often a mild disorder but otherwise similar to published clinical cases. Increased morbidity is significantly associated with bilineality. The frequency and impact of bilineality raise questions about possible assortative mating, the prevalence of TD, and assumed mechanisms of transmission and etiology.
McMahon
W M
WM
Department of Psychiatry, University of Utah, Salt Lake City 84132, USA.
van de Wetering
B J
BJ
Filloux
F
F
Betit
K
K
Coon
H
H
Leppert
M
M
D000293:Adolescent; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D002648:Child; D005260:Female; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008875:Middle Aged; D008957:Models, Genetic; D009771:Obsessive-Compulsive Disorder / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D010375:Pedigree; D010641:Phenotype; D012307:Risk Factors; D005879:Tourette Syndrome / Q000175:diagnosis / Q000235:genetics* / Q000523:psychology