Immunological studies of patients with Down's syndrome. Measurements of autoantibodies and serum antibodies to dietary antigens in relation to zinc levels.

Recurrent diarrhoea and weight loss in many adult patients with Down's syndrome (DS), initiated a search for malabsorption based on determination of serum IgG and IgA antibody levels to dietary antigens. The results were compared with measurements of autoantibodies and serum zinc levels. DS patients had increased IgG and IgA activities to gluten proteins, casein and ovalbumin compared with an age- and sex-matched group of other mentally retarded patients in the same institution. Intestinal biopsy was performed in six of the 38 patients; one had total and one partial villous atrophy. Serum zinc was significantly lower in DS patients (median 14.7 mumol/l, range 5.5-20 mumol/l) than in the controls (median 16.4 mumol/l, range 12.7-19.5 mumol/l). DS patients with increased IgA activity to gluten weighed less and had lower concentrations of zinc in serum than DS patients with normal IgA activity. Twenty-eight per cent of the DS patients had autoantibodies to the thyroid gland. Our results suggest intestinal malfunction in DS, perhaps related to a defect of immune regulation caused by reduced levels of zinc in serum.