The immunofluorescent "band" test in mixed connective tissue disease.

Skin biopsy specimens from normal subjects and patients with mixed connective tissue disease, systemic lupus erythematosus, and rheumatoid arthritis were examined for the presence of a "band" of immunoglobulins and complement at the dermal-epidermal junction, using immunofluorescent techniques. A positive immunofluorescent band test was found in the clinically uninvolved skin in three of six patients with mixed connective tissue disease, five of six patients with systemic lupus erythematosus, and none of the patients with rheumatoid arthritis or normal subjects. Although a positive immunofluorescent band test in uninvolved skin has been considered to be fairly specific for the diagnosis of systemic lupus erythematosus, our results suggest that this test cannot be used to distinguish mixed connective tissue disease from systemic lupus erythematosus.