Lupus Erythematosus Tumidus Mimicking Erythema Nodosum: A Diagnostic Challenge.

Lupus erythematosus tumidus (LET) is an uncommon variant of cutaneous lupus that may clinically resemble other inflammatory dermatoses, leading to diagnostic delay. We report the case of a 36-year-old woman with a four-year history of recurrent erythematous nodules initially diagnosed as erythema nodosum. Serologic evaluation revealed a strongly positive antinuclear antibody (1:1280) and elevated anti-double-stranded DNA (1:160) titers. Given persistent symptoms and incongruent clinical findings, a repeat skin biopsy was performed and confirmed the diagnosis of tumid lupus. Treatment with hydroxychloroquine resulted in complete resolution of cutaneous lesions and normalization of serologic markers. This case highlights the potential for atypical presentations of LET and underscores the importance of histopathologic confirmation when the clinical course is inconsistent with the initial diagnosis.