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

INTRODUCTION: Eosinophilic annular erythema (EAE) is an inflammatory dermatosis characterized clinically by pruritic annular erythematous lesions and histopathologically by eosinophilic dermal infiltration, usually without flame figures. 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 1-month history of annular erythema that was refractory to topical corticosteroids 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), 1,959 pg/mL, with no autoantibodies. Histopathological examination of annular erythema revealed dense perivascular infiltration of eosinophils in the superficial dermis. After exclusion of major differential diagnoses, a diagnosis of EAE was established. Low-dose systemic corticosteroid therapy was initiated but the disease was exacerbated with increasing serum TARC level of 17,310 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: This single case suggests that serum TARC levels may reflect disease activity in EAE. However, further studies are needed to determine whether TARC can serve as a reliable disease activity biomarker in this disease.