Diagnostic significance of immunohistological skin examination in patients with primary Sjögren's syndrome and other chronic inflammatory connective tissue diseases.

Clinically unaffected skin from 57/84 (68%) patients with primary Sjögren's syndrome (primary SS) was found to contain intraepidermal in vivo deposits of IgG, using a direct immunofluorescence technique. Similar IgG deposits were found in only 4/26 (14%) patients with secondary SS, in 3/28 (11%) patients with rheumatoid arthritis without SS (RA), in 2/13 (15%) patients with systemic lupus erythematosus without SS (SLE), in 10/41 (24%) patients with other well-defined connective tissue disease (CTD) and in 2/65 (3%) of normal controls (p less than 0.001 for all groups compared to primary SS). Intraepidermal IgG deposits were found in 5/12 (42%) patients with incipient primary SS and in 6/15 (40%) patients with ill-defined CTD (NS). None of the patients with primary SS had immunoglobulin deposits in the dermo-epidermal junction zone, while this was observed in 12% of the patients with RA and in 20% of the patients with SLE. We conclude that the presence of intraepidermal IgG deposits is valuable in the differential diagnosis between primary SS and RA or SLE, even if RA and SLE are complicated with SS. Examination for intraepidermal IgG deposits should supplement the lupus band test.