Erythema Multiforme-Like Fixed Drug Eruption During Azathioprine and Hydroxychloroquine Treatment for Systemic Lupus Erythematosus Mimicking Rowell Syndrome: A Rare and Challenging Clinical Scenario.

Background. Fixed drug eruption and Rowell syndrome stand as intriguing entities with overlapping clinical and pathological features. Case Presentation. A 32-year-old female patient presented with a tender and pruritic rash on the left upper chest for 3 days. Clinical examination revealed a flaring rash on the chest, under her left eye, tongue, and lips. The patient had a significant past medical history of systemic lupus erythematous with positive (ANA, Sm, dsDNA, ribosomalP, RNP) antibodies, hypocomplementemia, inflammatory arthritis, discoid lupus, leukopenia, thrombocytopenia, and immune thrombocytopenic purpura, and avascular necrosis affecting both hips and her right knee. At the time of presentation, the patient was on azathioprine 150 mg daily and hydroxychloroquine 200 mg twice daily. Skin biopsy of the left upper chest revealed interface dermatitis with necrotic keratinocytes at the dermal-epidermal junction. Superficial and, in some areas, deep perivascular and peri adnexal lymphocytic infiltrates were observed, accompanied by eosinophils. CD123 staining highlighted 16% of the inflammatory cells. Direct Immunofluorescence for IgG, IgA, IgM, C3, and fibrinogen revealed positive linear basement membrane staining for IgG and fibrinogen, with no significant staining for the remaining immunoreactants. Considering the patient's history of medicine usage, and negative SS-A and SS-B antibody, a fixed drug eruption was favored. Discussion. This article discusses the clinical presentations, pathophysiological mechanisms, and diagnostic criteria for fixed drug eruption and Rowell syndrome. Conclusion. Awareness of the distinct clinical and histopathologic features of fixed drug eruption and Rowell syndrome, particularly when sharing cutaneous manifestations, underscores the importance of a comprehensive diagnostic approach and laboratory testing. [ABSTRACT FROM AUTHOR]