Conversion of discoid lupus erythematosus to mixed connective tissue disease.

The progression from discoid lupus erythematosus (DLE) to severe systemic lupus erythematosus (SLE) is rare. Two patients with DLE for five and 10 years eventually developed systemic involvement with clinical features of mixed connective tissue disease (MCTD). Both patients had high titer serum antibody to ribonucleoprotein (RNP) and epidermal nuclear staining on direct immunofluorescence of normal skin. Neither patient had renal disease but one patient developed pulmonary involvement. This observation suggests that patients with DLE and the Raynaud phenomenon may have a connective tissue disease subset characterized by anti-RNP, the immunologic marker for MCTC.