An immunofluorescence study of pityriasis lichenoides.

In a study of 27 patients with pityriasis lichenoides IgM and C3 have been observed on direct immunofluorescence of fresh lesions. Other immunoglobulins and complement components were not observed. Immunofluorescence was seen in 31 (72%) of 43 fresh lesions. It occurred in the walls of superficial dermal vessels and along the dermal-epidermal junction. This pattern of immunofluorescence appears to be characteristic of the disease. Uninvolved skin showed the immunofluorescence less frequently and old scaly lesions none. The concept that pityriasis lichenoides is an immune complex disorder is discussed.