Specific IgE and skin tests to house dust and storage mites and eosinophil cationic protein in scabies

Background In addition to the infestation with scabies mites also allergic IgE mediated mechanisms play a role in the pathogenesis of scabies. Aim The aim of this study was to answer the question whether specific IgE mediated reactions to house dust and storage mites can be found and whether eosinophils are involved in the pathogenesis of scabies. Material 44 scabies patients (12 children. 32 adults) were classified according to the extent of skin involvement as mild, moderate and severe. Age- and sex-matched healthy controls and patients with atopic dermatitis were studied for comparative purposes. Methods Total and specific IgE to Dermatophagoides pteronyssinus, D. farinae, Acartis siro and Pityrosporon ovale were tested by CAP-FEIA (Pharmacia. Sweden) before and 6 weeks after treatment and prick tests were performed with the same allergens. The number of eosinophils in the peripheral blood and tissue specimens was counted and the eosinophil cationic protein (ECP) was determined by CAP-FEIA in serum before and 6 weeks after therapy. Results The total IgE was increased in 86% of patients. It was correlated with the extent of skin involvement (p < 0.05) and was significantly less increased 6 weeks after treatment (p < 0.115). Specific IgE to house dust and storage mites was increased up to 48% in the CAP-EEIA and up to 61% in the prick test, all together significantly higher than in controls and in comparable frequencies with atopic dermatitis. Pityrosporon ovate IgE was within normal ranges. Die ECP levels were increased in 89% of patients and correlated only in mild versus moderate or severe extent of the disease. 6 weeks after treatment, however, they were significantly less increased (p < 1.01). In addition. ECP levels were correlated with the IgE levels in scabies (C = 0.88). The number of eosinophils in the peripheral blood was increased in 64% of cases and in tissue specimens in 84% of cases studied. In principle, the extent of skin lesions was milder and the frequencies of specific IgE in the CAP- and prick test as well as the levels of total IgE (p < 0.01) and ECP (only in the tendency) were lower in children than in adults. Discussion The frequencies in the total and specific IgE to house dust and storage mites are comparable with those in atopic dermatitis. The question remains open, whether this is due to cross reactivity with scabies mites or whether this suggests an enhanced susceptibility to generalized scabies eruption. The increase in the ECP and its correlation to IgE, its decline after treatment (p < 0.05) and the occurrence of eosinophils in the peripheral blood and in inflammatory infiltrates of the skin suggest the involvement of eosinophils in the pathogenesis of scabies as an ectoparasitic IgE mediated disease.