Subacute cutaneous lupus erythematosus versus systemic lupus erythematosus: diagnostic criteria and therapeutic implications.

Background: The nosologic position of subacute cutaneous lupus erythematosus (SCLE) is controversial. More than four American Rheumatism Association (ARA) criteria for systemic lupus erythematosus (SLE) are found in a proportion of patients diagnosed as having SCLE; thus such cases could be classified as SLE.
Objective: Our purpose was to determine whether ARA criteria for SLE are helpful in differentiating SCLE from SLE and whether cutaneous and visceral changes, immunologic findings, and photosensitivity provide a basis for diagnosis of SCLE.
Methods: A cohort of 143 patients (79 with SCLE, 58 with SLE, and six with overlapping features of SCLE and SLE) was studied clinically, histologically, and immunologically as well as by phototesting. The patients were observed for up to 10 years, and the course of the disease and response to therapy were evaluated in each group.
Results: SCLE differed from SLE by cutaneous changes, significantly less frequent kidney involvement, serositis and arthritis, and the rare presence of double-stranded DNA, U1RNP, and Sm antibodies characteristic of SLE. Ro(SS-A) and La(SS-B) antibodies were detected with similar frequency, and photosensitivity was not related to the presence of Ro antibody. In contrast, photoreproduction (appearance of LE lesion in irradiated area) was significantly more frequent in patients with SCLE. The course of SCLE in older patients was less severe than in younger patients, and aggressive therapy was usually not required.
Conclusion: Patients with SCLE (although the majority fulfill more than four ARA criteria for SLE) show significant differences from those with SLE in terms of cutaneous and visceral involvement, immunologic findings, photosensitivity, course of the disease, and the requirement for therapy. Therefore SCLE should be recognized as a separate subset. However, cases of overlapping SLE and SCLE suggest a close relation.