Comorbidity of Tourette's syndrome and schizophrenia--biological and physiological parallels.

The authors report on five patients who first developed Tourette's syndrome (TS) and later schizophrenia with the typical positive and negative symptoms; all five had an unfavorable course of schizophrenia. These observations as well as other reported cases raise the question of whether both disorders may share a common background. This is discussed under the aspects of similar symptomatology (echolalia, motor symptoms, cognitive deficits, obsessive-compulsive symptoms), similar pathophysiological signs, genetics and signs of an underlying inflammatory process in subgroups of cases, as well as common therapeutic strategies. A genetically determined susceptibility could possibly underlie both disorders, e.g., an autoimmunologically triggered inflammation or a common pathophysiology of certain symptoms. Both disorders show disturbances of the multiple functional pathways, which seem to be involved in the pathophysiology of both. The clinical overlap of TS and of schizophrenia may be due to a final common pathophysiological pathway.