Histologic and clinical findings in human scabies

The epidermal histological findings in the primary scabetic lesion are hyperkeratosis, acanthosis, and spongiotic edema and vesiculation. The dermal changes consist of perivascular and diffuse cell infiltrates, mainly mononuclear cells, and sometimes eosinophilic granulocytes. The number of mast cells are slightly greater in primary scabetic lesions compared with secondary lesions and normal skin. Vasculitis is found in those cases showing tissue eosinophils, severe dermatitis, and many mites. A nodular lesion shows perivascular infiltrates mainly containing histiocytes, some with atypical and hyperchromatic nuclei and a few in mitosis, and some lymphocytes and cells with pyroninophilic cytoplasm. Secondary scabetic lesions show acanthosis and perivascular inflammatory cell infiltrates, mainly mononuclear cells, whereas clinically normal skin presents very slight perivascular and diffuse mononuclear cell infiltrates in half of the patients. Both the number of circulating eosinophilic granulocytes and serum IgE concentrations correlate with the severity of the skin reaction. Ten of 60 patients with scabies had markedly increased numbers of circulating eosinophilic granulocytes during scabies infestation. In most of the patients, however, the number of circulating eosinophils decreased after scabies treatment.