PKU-related dysgammaglobulinaemia: the effect of diet therapy on IgE and allergic sensitization

The effect of diet on the development of immunoallergic signs and symptoms in children with phenylketonuria (PKU) was evaluated. Immunological indices of 58 children with PKU treated with diets were compared to the immunological indices of 58 healthy (non-PKU) children. In the PKU group, 39 children had been placed on diet therapy within the first month of life; 19 children had been placed on diet therapy after 6 months of age. Total circulating lymphocytes; CD3+, CD4+, CD8+ circulating lymphocytes; and serum IgA, IgM, IgG and total IgE levels were measured for each child. Skin prick tests were performed for common inhalant and food allergens. Every 3 months over the 2-year period of this study, the signs and symptoms of eczema, allergic rhinitis and asthma were recorded. The PKU group had lower IgG levels (p=0.004) and higher total IgE levels (p=0.0001) than the control group. Significantly lower IgE levels were found in children started on diet therapy within the first month of life compared with those started on diet therapy after 6 months of age (p=0.0001). Allergic sensitization was significantly more frequent in the PKU group (24/58 vs 13/58, z=2.00, p<0.05), but no significant difference in the incidence of eczema and allergic rhinitis was found. Asthma was less frequent in the PKU group than in the control group (5/58 vs 14/58, z=2.09, p<0.05). Thus, diet appeared to prevent the development of immunoallergic signs and symptoms.