Pityriasis rosea. An immunologic study.

Some immunologic studies were carried out for 31 patients with pityriasis rosea. Normal levels of serum IgG and IgA but higher levels of IgM were obtained. Serum C3 values were decreased while C4 values were normal. B lymphocytes showed no difference from the controls, whereas T-cell counts were significantly lower in the patients. The migration inhibition indices were higher in the patients than the controls. Direct immunofluorescence tests were negative in the studied three cases. The possible implication of a viral infection in the production of the reported changes was discussed.