Familial aggregation of psychotic symptoms in Huntington's disease

OBJECTIVE

The mutation responsible for Huntington's disease is an elongated and unstable trinucleotide (CAG) repeat on the short arm of chromosome 4. Psychotic symptoms are more common in patients with Huntington's disease than in the general population. This study explored the relationship of psychosis in Huntington's disease patients with the number of CAG repeats and family history of psychosis.

METHOD

Forty-four patients with Huntington's disease, 22 with and 22 without psychotic symptoms, were recruited from two university-affiliated medical genetics clinics in Seattle and Vancouver, B.C. Psychiatric assessments of the subjects were made through chart review, and diagnoses were validated by structured interviews in a subset of patients. The demographic and clinical characteristics of the psychotic and nonpsychotic patients were compared.

RESULTS

The two groups did not differ in demographic and clinical characteristics, except that subjects with psychosis were significantly more likely than nonpsychotic subjects to have a first-degree relative with psychosis. In eight of nine families in which Huntington's disease probands with psychosis had a first-degree relative with psychosis, the relative's psychosis co-occurred with Huntington's disease. In the Huntington's disease probands with psychosis, the onset of psychosis correlated with the onset of the neurological symptoms of Huntington's disease, and the age at onset of psychosis was lower in probands with a higher number of CAG repeats.

CONCLUSIONS

Patients with Huntington's disease and psychotic symptoms may have a familial predisposition to develop psychosis. This finding suggests that other genetic factors may influence susceptibility to a particular phenotype precipitated by CAG expansion in the Huntington's disease gene.

Effects of swimming exercise on the pathogenesis of acute murine Toxoplasma gondii Me49 infection

The effects of swimming exercise on the pathogenesis of acute murine toxoplasma infection were studied. Swimming (45 min/day) initiated on the day of inoculation with the avirulent Me49 strain of Toxoplasma gondii did not alter survival of infected mice. At a later stage of infection, daily swimming appeared to promote the recovery of appetite and weight gain. Immune activation was apparent in toxoplasma-infected mice, and swimming blunted splenic enlargement but not the respiratory burst activity of peritoneal exudate cells. Infection caused a significant elevation of serum tumor necrosis factor (TNF) levels which was attenuated by a daily swimming program. These data show that swimming exercise is not deleterious to mice acutely infected with T. gondii Me49 and that the more rapid recovery in exercised mice is associated with reduced serum TNF levels.

Stress and pathogenesis of infectious disease

Despite inherent difficulties in defining and measuring stress, a scientific framework has been provided in recent years for understanding how disruptive life experiences might be translated into altered susceptibility to infectious diseases. Studies of the effects of stress on pathogenesis of infectious disease are highly relevant to assessment of the biological importance of the immune impairments that have been associated with stress. With a few notable exceptions, investigations of viral infections in humans and in animal models support the hypothesis that stress promotes the pathogenesis of such infections. Similar conclusions can be drawn from studies of bacterial infections in humans and animals and from a small number of studies of parasitic infections in rodent models. While many of these studies have substantial limitations, the data nonetheless suggest that stress is a potential cofactor in the pathogenesis of infectious disease. Given recent unprecedented advances in the neurosciences, in immunology, and in the field of microbial pathogenesis, the relationship between stress and infection should be a fruitful topic for interdisciplinary research.