A Case Report of Eosinophilic Annular Erythema Treated with Dapsone and Associated Changes in Serum TARC Levels

Introduction: Eosinophilic annular erythema (EAE) is an inflammatory dermatosis characterized clinically by annular erythematous lesions and histopathologically by eosinophilic infiltration in the dermis. To date, neither standardized therapeutic guidelines nor established biomarkers reflecting disease activity have been identified. Case Presentation: A 50-year-old woman was referred to us with a one-month-history of annular erythema that was refractory to topical corticosteroid and antihistamines. The patient had no medical history of any diseases including bronchial asthma and allergic rhinitis, beyond rectal cancer. The patient did not take any medicines including dietary supplements. Physical examination showed annular erythematous lesions on the lower extremities and trunk. Blood examination showed eosinophil count of 500/µL and thymus and activation-regulated chemokine (TARC), 1959 pg/mL, with no autoantibodies. Histopathological examination of annular erythema revealed dense perivascular infiltration of eosinophils in the superficial dermis. After excluding tinea corporis, bullous pemphigoid, eosinophilic granulomatosis with polyangiitis, connective tissue diseases, and dermadromes associated with internal malignancies, a diagnosis of EAE was established. Low dose of systemic corticosteroid therapy was initiated but the disease was exacerbated with increasing serum TARC level of 17310 pg/mL. However, the addition of dapsone at 50 mg/day to prednisolone at 0.5 mg/kg/day resulted in rapid resolution of newly developed lesions along with decreased serum TARC level, allowing for subsequent tapering and discontinuation of corticosteroid. Conclusion: The parallel changes observed between cutaneous disease activity and serum TARC levels during the clinical course suggest that TARC may serve as a potential biomarker reflecting disease activity in EAE.