Failure to detect immune complexes in the secondary stage of pityriasis rosea.

Thirty-three patients with pityriasis rosea were studied with regard to the possible presence of circulating and cutaneously deposited immune complexes. The levels of circulating immune complexes, determined by a solid-phase C1q-binding assay, were not different from those of healthy control individuals. The levels were similar in samples obtained during the initial and during the remission stages of the disease. Cutaneous deposits of immunoglobulin and/or complement were found in only 5 of 33 patients. This study does not support of concept that circulating immune complexes are important for the development of the secondary skin lesions in pityriasis rosea.