Subacute cutaneous lupus erythematosus and discoid lupus erythematosus. Comparative histopathologic findings.

Subacute cutaneous lupus erythematosus (SCLE) is a recently described distinct subset of lupus erythematosus (LE) having characteristic clinical, serologic, and genetic findings. This study describes the histopathologic characteristics of SCLE and determines whether it could be differentiated from discoid lupus erythematosus (DLE) on histopathologic grounds alone. Biopsy specimens from 33 patients having either SCLE or DLE, as defined by strict clinical criteria, were examined without knowledge of the clinical diagnosis. Histologic discrimination between SCLE and DLE was accomplished in 82%. The specimens from DLE lesions had substantially more hyperkeratosis, basement membrane thickening, follicular plugging, and superficial and deep inflammatory cell infiltrate, while SCLE had more epidermal atrophy. The histopathologic differences between SCLE and DLE further support the concept that SCLE is distinct from DLE and should be considered a unique subset of LE.