Systemic lupus erythematosus and vasculitic urticaria. Effect of dapsone and complement levels.

Dapsone 100 mg daily led to a rapid and complete clearing of extensive vasculitic urticarial lesions in a female patient with systemic lupus erythematosus. Complement determinations revealed an intensive activation of the classical pathway before dapsone therapy. Normalization of CH50, C1 and C2 occurred during the treatment, whereas C3 and C4 remained lowered.