Eosinophilic Annular Erythema Associated With IgM Monoclonal Gammopathy of Undetermined Significance.

Eosinophilic annular erythema (EAE) is a rare inflammatory skin disease characterized by recurrent annular or figurate erythematous plaques and eosinophil-rich dermal infiltrates. Here, we present the case of a 73-year-old Japanese woman who had a 10-month history of pruritic annular and figurate plaques with central postinflammatory hyperpigmentation of the trunk and proximal extremities. Histopathological examination revealed dense perivascular and interstitial lymphocytic infiltrates with numerous eosinophils in the dermis, without vasculitis or flame figures, consistent with EAE. Laboratory evaluation revealed markedly elevated serum IgM, and immunofixation demonstrated an IgM-λ monoclonal protein with urinary λ-type Bence Jones protein. She was asymptomatic and had no evidence of end-organ damage, including hypercalcemia, renal insufficiency, anemia, or bone lesions. Additionally, the hematologic findings were consistent with a diagnosis of IgM monoclonal gammopathy of undetermined significance. The eruption regressed with high-potency topical corticosteroids, and the patient was managed with dermatological therapy and hematological surveillance. Reports of EAE associated with IgM monoclonal gammopathy are scarce. This case highlights that EAE may coexist with IgM monoclonal gammopathy and supports hematological evaluation and follow-up when IgM monoclonal proteins are detected.