Lupus Panniculitis of the Buttock: A Refractory Case With Diagnostic Challenges.

Lupus erythematosus panniculitis (LEP) is a rare form of chronic cutaneous lupus involving the subcutaneous fat. Ulcerative lesions are uncommon and may mimic infectious, inflammatory, or neoplastic disorders, leading to delayed diagnosis. We report the case of a 40-year-old woman with longstanding photosensitivity who presented with a painful left gluteal ulcer evolving over eight months. The lesion began as a deep inflammatory nodule and progressively ulcerated. Antibiotic therapy was ineffective. Laboratory tests showed positive antinuclear antibodies at 1:160 and positive anti-Sm/RNP antibodies, with negative anti-double-stranded DNA antibodies. Histopathology revealed lymphocytic lobular panniculitis consistent with lupus panniculitis. Treatment with hydroxychloroquine and systemic corticosteroids resulted in partial improvement, but relapses occurred during steroid tapering. Dapsone failed to control the disease. Methotrexate was subsequently introduced, leading to marked clinical improvement within three months. This case highlights an unusual ulcerative gluteal presentation of lupus panniculitis. Early biopsy and clinicopathological correlation are essential to exclude mimickers and guide appropriate immunomodulatory treatment.