A Case of Cutaneous Arteritis Presenting as Infiltrated Erythema in Eosinophilic Granulomatosis With Polyangiitis: Features of the Unique Morphological Evolution of Arteritis as a Diagnostic Clue.

Eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome) is a rare systemic vasculitis affecting small- and medium-sized vasculature, associated with asthma and eosinophilia. Different levels of vasculitis in cutaneous lesions have been observed, including dermal small vessel vasculitis and subcutaneous muscular vessel vasculitis. Although the EGPA-associated small vessel vasculitis described as leukocytoclastic vasculitis can be often found in the documented literature, the features of subcutaneous muscular vessel vasculitis in EGPA-associated cutaneous lesions have been rarely demonstrated clinically and histopathologically in English literature. Herein, we report a case of EGPA involving infiltrated erythema on the extremities, with different stages of cutaneous arteritis characterized by eosinophilic arteritis and granulomatous arteritis in the same affected artery. We present this as a unique diagnostic clue for EGPA.