When typical is atypical: mycobacterial infection mimicking cutaneous vasculitis.

Patients with systemic lupus erythematosus (SLE) who present with skin disease pose the clinician with diagnostic challenges. The skin disease can reflect an increase in systemic disease activity suggested by other features of active lupus and, as such, usually responds well to more aggressive immunosuppressive therapy. Other possibilities of skin disease include drug eruptions, skin disease unrelated to SLE and, more rarely, opportunistic skin infection. In patients who show a poor response to more aggressive immunosuppressive therapy, consideration must be given to the possibility of opportunistic infection. A high index of suspicion will allow prompt treatment. We describe two patients with SLE who developed cutaneous atypical mycobacterial infection during immunosuppressive therapy. The diagnosis of cutaneous vasculitis was considered in both cases, but subsequent skin biopsy revealed the correct diagnosis. This report illustrates the importance of skin biopsy in patients with suspected cutaneous lupus who are not responding to immunosuppressive therapy.