Crusted scabies: clinical and immunological findings in seventy-eight patients and a review of the literature.

To describe the clinical and immunological features of crusted scabies in a prospectively ascertained cohort of 78 patients. All patients requiring inpatient treatment for crusted scabies in the 'top end' of the northern territory of Australia over a 10 year period were prospectively identified. Demographics, risk factors, and immunological parameters were retrospectively compiled from their medical records and pathology databases. More than half the patients with crusted scabies had identifiable immunosuppressive risk factors. Eosinophilia and elevated IgE levels occurred in 58% and 96% of patients, respectively, with median IgE levels 17 times the upper limit of normal. Seventeen percent had a history of leprosy but 42% had no identifiable risk factors. There was a decrease in mortality after the introduction of a treatment protocol consisting of multiple doses of ivermectin combined with topical scabicides and keratolytic therapy. Crusted scabies often occurs in patients with identifiable immunosuppressive risk factors. In patients without such risk factors, it is possible that the crusted response to infection results from a tendency to preferentially mount a Th2 response. The treatment regime described was associated with a reduction in mortality. This is the largest reported case series of crusted scabies.