The progressive systemic sclerosis/systemic lupus overlap: an unusual clinical progression.

Three patients with the unusual combinations of discoid lupus, systemic lupus erythematosus (SLE), and progressive systemic sclerosis (PSS) are reported. The first patient developed PSS eight years after a diagnosis of discoid lupus had been made and this was complicated by myositis six years later. The second patient developed PSS more than 20 years after being diagnosed as having SLE. The third patient developed SLE with predominant features of urticarial vasculitis six years after PSS. Mild myositis also ensued. There were no antibodies to U1RNP demonstrable in any of these patients. The clinical progression of SLE to PSS or vice versa in the absence of features of mixed connective tissue disease is distinctly uncommon.