Churg‐Strauss syndrome with coexistence of eosinophilic vasculitis,granulomatous phlebitis and granulomatous dermatitis in bullous pemphigoid‐like blisters

The main histopathological features in the cutaneous lesions of Churg‐Strauss syndrome (CSS) are dermal leukocytoclastic vasculitis with a variable eosinophilic infiltrate and non‐vasculitic tissue eosinophilia with granuloma formation. This wide histopathological spectrum may account for the various skin manifestations of CSS. However, the unique histopathological combination of dermal eosinophilic vasculitis and subcutaneous granulomatous phlebitis accompanied by bulla formation has not been previously described. We report an unusual CSS case showing dermal necrotizing eosinophilic vasculitis and granulomatous phlebitis in purpuric lesions coupled with subepidermal blistering. The blisters showed dermal granulomatous dermatitis and eosinophilia without evidence of vasculitis. Dermal necrotizing eosinophilic vasculitis was characterized by fibrinoid alteration of the vessel wall, a prominent perivascular eosinophilic infiltrate, a few infiltrating histiocytes along the affected vessel wall, and the absence of neutrophilic infiltration. The underlying subcutaneous granulomatous phlebitis was characterized by an angiocentric histiocytic infiltrate surrounded by marked eosinophilic infiltrate. Deposition of cytotoxic proteins and radicals derived from eosinophils in the vessel walls and papillary dermis followed by a secondary granulomatous response may account for the unique clinical and histopathological features in this case. Ishibashi M, Kudo S, Yamamoto K, Shimai N, Chen K‐R. Churg‐Strauss syndrome with coexistence of eosinophilic vasculitis, granulomatous phlebitis and granulomatous dermatitis in bullous pemphigoid‐like blisters.