The genetics of Tourette syndrome.

Tourette syndrome is a complex neurological disorder that usually becomes evident between 4 and 18 years of age. The disorder is characterized by chronic motor and phonic tics, often with a variety of behavioural comorbidities; in particular, attention-deficit hyperactivity disorder, obsessive-compulsive disorder, and impulse control disorder. The cause of Tourette syndrome is poorly understood. Although environmental factors are proposed to have a role, genetic factors are thought to be the primary contributors to the pathogenesis of this disorder. However, identification of the causative gene mutations or risk alleles has proved to be difficult. Early studies on the genetics of Tourette syndrome focused on multigenerational lineages and suggested Mendelian inheritance, but subsequent segregation analyses point to a more-complex inheritance pattern. A monogenic inheritance model has been proposed following the identification of rare genetic mutations associated with the Tourette syndrome phenotype. Although no specific mutations have found to directly cause Tourette syndrome, genetic findings may enable identification of the affected pathways, and could lead to the development of new treatment strategies. In this Review, we provide an overview of the genetics of Tourette syndrome and highlight how this knowledge has improved our understanding of the possible pathogenic mechanisms of this neurological disorder.