Subacute Cutaneous Lupus Erythematosus Triggered by Radiotherapy
A 72-year-old woman underwent breast cancer surgery and received adjuvant systemic treatment with the estrogen receptor antagonist tamoxifen 20 mg/day, which was discontinued after the patient developed a generalized skin rash about two weeks after the initiation of tamoxifen. This rash was clinically and histologically diagnosed as erythema exsudativum multiforme, which rapidly resolved under systemic treatment with prednisolone. Tamoxifen was discontinued. The patient afterwards received radiotherapy of the left breast. A cumulative dose of 40 Gy in 15 fractions was administered and was initially well tolerated by the patient. After finishing radiotherapy, our patient developed a painless maculopapular erythema on the left breast limited to the irradiated area.\nHistology of a skin biopsy taken from the left breast showed an acute interface dermatitis with vacuolization of the dermo-epidermal junction, apoptotic keratinocytes in the basal epidermis and a mild, predominantly lymphocytic, infiltrate within the superficial dermis and with few admixed neutrophils and eosinophilic granulocytes.\nThese histological changes were consistent with subacute cutaneous lupus erythematosus (SCLE). Because of the presence of eosinophilic granulocytes in the inflammatory infiltrate, a fixed drug eruption was considered a differential diagnosis. An allergic reaction to tamoxifen was ruled out by a negative scratch-patch test.\nSerology revealed elevated titers for antinuclear antibodies 1:2,560, anti-SS-A at >3,400 U/ml, anti-SS-B at >3,400 U/ml and rheumatoid factor at 41 IU/ml. Complement components (C3 and C4) were within normal limits and urine analysis was unremarkable.\nBased on the patient's history, the clinical presentation of the skin lesions, serologic results, histopathology and allergy testing, a diagnosis of SCLE – presumably triggered by radiotherapy – was made.\nThe administration of topical corticosteroids and systemic hydroxychloroquine at 400 mg/day led to a total disappearance of the lesions on the left breast within 6 weeks.