Lupus and non-lupus cutaneous manifestations in systemic lupus erythematosus.

Mucocutaneous manifestations occur frequently in systemic lupus erythematosus (SLE). Common non-lupus dermatoses may be confused with lupus rashes, with important clinical consequences. A study of 84 consecutive patients with SLE was performed to determine the comparative frequency of lupus and non-lupus mucocutaneous abnormalities, the comparative sensitivity of routine histology and immunofluorescence in the diagnosis of lupus rashes, and the association of skin manifestations with other clinical and serological features. Thirty-five patients had dermatoses attributable to SLE (mean 3.7 per patient) and 58 had dermatoses which were not directly attributable to SLE (mean 2.1 per patient), highlighting the need for accurate diagnosis of skin rashes in SLE patients. Routine histology confirmed the clinical diagnosis of typical cutaneous lupus in 100% of malar lupus rashes and in approximately 90% of subacute cutaneous and discoid lupus rashes. Direct immunofluorescence of the affected skin provided supportive evidence of cutaneous lupus in 60% of malar lupus rashes and approximately 50% of subacute cutaneous and discoid lupus rashes. This reaffirmed the poor sensitivity of immunofluorescence, compared with routine histology, in the diagnosis of lupus rashes. The association of subacute cutaneous lupus with anti-Ro antibodies was confirmed.