Although family and twin studies suggest that genetic factors are involved in the etiology of Tourette syndrome and other related tic disorders, further evidence is needed to demonstrate that the familial transmission is consistent with known genetic factors. We performed a complex segregation analysis that allowed for a variable age of onset of Gilles de la Tourette, other tic disorders and obsessive compulsive phenotype information on 108 extended families, each ascertained through one Tourette proband by using regressive models that are able to incorporate additional explanatory variables and major gene effects. A special version of the S.A.G.E. program, REGTLhunt, was used to explore the likelihood surface of all examined models. Results indicated that the pattern of Tourette and other related tic disorders in our data sample is not consistent with Mendelian inheritance even after modelling explanatory variables such as obsessive compulsive symptomatology.

The aim of this study was to assess rates for tic disorders and obsessive compulsive psychopathology in families of children and adolescents with Gilles de la Tourette syndrome (TS). Diagnoses were based on the DSM III-R criteria. Obsessive compulsive psychopathology, that did not fulfill the criteria for obsessive compulsive disorder (OCD) was additionally assessed and termed obsessive compulsive symptoms (OCS). The authors hypothesized that comorbid OCD or OCS in TS patients predicts a higher familial loading with obsessive compulsive symptomatology. The study cohort included 87 patients with TS who were evaluated clinically and with the use of a structured psychiatric interview. All available parents (152/174; 87%), several sibs (49/93; 53%) and some second degree relatives (27/659; 4.1%) were also interviewed. For other first and second degree relatives the family history method was used. Familial rates for TS were clearly elevated. Rates for chronic tic disorders (CT) were considerably lower than in previous studies. Additionally, tic disorders not otherwise specified (TDNOS) were diagnosed in a substantial number of first degree (15/267; 5.6%) and second degree relatives (36/659; 5.5%). OCD in parents (4/174; 2.3%) did not occur in an above baseline rate. However, both OCD (14/87; 16.1%) and OCS (15/87; 17.2%) were frequently associated with TS in index patients. Interestingly, 10 of 16 fathers with OCS also had a tic disorder. Obsessive compulsive psychopathology clustered in families. It is concluded that genetic studies in TS could profit from adhering to a conservative diagnostic approach to both tic disorders and OCD. The familial clustering of OCS/OCD in conjunction with the elevated paternal rate for the co-occurrence of tic disorders and OCS might indicate heterogeneity of TS.

Huntington's disease (HD) is a progressive, autosomal dominant disorder of the central nervous system characterized by motor, cognitive, and psychiatric abnormalities. The hallmark of HD is a distinctive choreie movement disorder that typically has a subtle insidious onset. The characteristic pathological features are neostriatal atrophy and neuronal loss. In vivo putamen and caudate volume measures revealed that the volume of the putamen and, to a lesser extent, of the caudate are reduced at early stages of the disorder, indicating atrophy of these basal ganglia nuclei (Harris et al., 1992). HD is caused by an expanded (CAG)n-repeat sequence near the 5' end of the respective gene (IT5), which maps to chromosome 4p16.3 (MacDonald et al. 1993). Molecular analysis of this repeat sequence revealed a range of 37-86 repeats in affected individuals and 11-34 repeats in normal controls (Duyao et al 1993). The number of repeats on the HD chromosome correlates negatively with the age at onset, regardless of sex of the transmitting parent.