Semiologic value of C1q and C4 cutaneous deposits. An immunofluorescent study

One hundred twenty skin biopsies from patients with different skin diseases were found to be positive for C3 cutaneous staining by immunofluorescence study. By the direct immunofluorescence method, we looked for C1q and C4 and immunoglobulin deposits in all those biopsies. C1q and/or C4 were only found in dermatoses with a recognised humoral immunologic mechanism; in some cases C1q and/or C4 deposits were found in the absence of immunoglobulins. The results showed that identification of C1q and C4 is important in routine immunopathologic studies, and provide interesting data of diagnostic value.