Viral immune complexes in systemic lupus erythematosus: C-type viral complex deposition in skin

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.

The specificity and clinical usefulness of the lupus band test

Granular deposition of immunoglobulin at the dermoepidermal junction is characteristic, but not pathognomonic, of lupus erythematosus. When rigid criteria for the lumpus band test are used, a positive result is highly specific. A positive band test is found in clinically normal skin and lesional skin of systemic lupus patients, and in lesional skin of discoid lupus patients. A positive band test is found infrequently in clinically normal skin of patients with other connective tissue disorders. Cutaneous lupus may be difficult to separate from other morphologically similar disorders. The lupus band test is useful in differential diagnosis because other disorders have either a specific pattern of immunoglobulin deposition or no immunoglobulin deposition. The mechanisms of immunoglobulin deposition at the epidermal basement membrane zone are discussed as well as pertinent clinical correlations of the positive band test.