SKIN-TEST AND RADIOALLERGOSORBENT TEST CHARACTERISTICS OF SCABIETIC PATIENTS

The scabies mite Sarcoptes scabiei and the Dermatophagoides house dust mites (HDM) are related phylogenetically and are the sources of sever al cross-reactive antigens. The purpose of this study was to investiga te the immune response to S. scabiei and HDM in scabietic patients. Sk in test sensitivity and serum IgE to both S. scabiei and HDM were dete rmined for patients who had or previously had confirmed ordinary scabi es. A retrospective group included nine subjects who had received succ essful treatment three weeks to one year prior to the study. A prospec tive group included 16 subjects with active scabies. Allergic historie s were obtained, serum was collected, and skin prick tests (SPTs) were performed at enrollment for all and periodically over the next 12 mon ths for the prospective patients. None of the individuals in either gr oup reported a known sensitivity to HDM. Six of the nine retrospective patients were SPT positive to both S. scabiei and HDM and two of thes e showed circulating IgE specific for these antigens. At diagnosis, 13 of 16 patients with active scabies were SPT positive to S. scabiei an d 12 of these were also SPT and/or radioallergosorbent test positive t o HDM. Six patients had circulating IgE directed at both S. scabiei an d HDM antigens while one subject had IgE to S. scabiei only and anothe r had IgE directed at HDM only. Twelve of the 15 subjects tested also showed IgE and/or IgG binding to one or more bands on Western blots of an S. scabiei-specific protein fraction. This study indicated that ap proximately half of the patients with active scabies had S. scabiei-an d HDM-specific circulating IgE while most patients cured of scabies la cked S. scabiei-and HDM-specific serum IgE. The data also suggested th at antibodies to S. scabiei in scabietic patients also recognize HDM; however, some antibodies were directed at scabies-specific antigens.