Tourette's syndrome and 'PANDAS' - Will the relation bear out?

Despite strong evidence of the importance of hereditary factors in the etiology of Tourette's syndrome (TS), research findings have consistently pointed to a role of environmental influences. A recent line of research has suggested that tic disorders and associated behavioral disturbances, such as obsessive-compulsive disorder, might develop following streptococcal infection by the process of molecular mimicry, whereby antibodies directed against bacterial antigens cross-react with brain targets. Such investigations have given rise to the notion that there is a spectrum of childhood neurobehavioral disorders (termed pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection [PANDAS]) that arise by postinfectious autoimmune mechanisms. This article reviews research results supporting the concept of PANDAS and discusses their limitations. Well-designed and adequately controlled studies are needed to determine whether there is a true etiologic relation between streptococcal infection and the onset or exacerbation of childhood neuropsychiatric disorders and whether the use of immune-modifying therapies for these conditions is rational.