Clq deposits at the dermoepidermal junction: a marker discriminating for discoid and systemic lupus erythematosus.

Discoid lupus (DL) and systemic lupus erythematosus (SLE) patients have been comparatively evaluated for complement and immunoglobulin deposits at the dermoepidermal junction (DEJ) by immunofluorescence (IF). When IF was positive, Clq deposits were quasi-constantly found in SLE patients with or without skin lesions (90%), while Clq was found in only 29% of the DL patients. Of the 42 DL patients followed-up to at least 2 years, 4 have eventually evolved a systemic disease. In these 4, neither cryoglobulinemia nor significant titers of ANA had been found at the time of presentation. Only 1 of these 4 patients had initially circulating immune complexes (P.E.G) and a positive IF in a normal sunprotected area. Clq deposits at the DEJ were present in all these 4. Of the remaining 38 DL patients, none has progressed to SLE: 8 had had significant titers of ANA, 5 had had circulating immune complexes, and 3 others had had cryoglobulinemia. Thus Clq deposits in DL cases are associated with a relatively high incidence of eventual systemic disease. Taken together, these data suggest that Clq deposits in skin may be a marker for systemic lupus.