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Competing Interests: The authors declare no conflicts of interest.

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.

Background: The diverse histopathologic spectrum of cutaneous vasculitis in eosinophilic granulomatosis with polyangiitis (EGPA, Churg-Strauss syndrome) has not been well described., Methods: Fifteen skin biopsy specimens from 9 EGPA patients with histopathologically proven necrotizing vasculitis were reviewed clinicopathologically., Results: Among 8 patients with dermal small vessel vasculitis, neutrophilic vasculitis was observed in 2 myeloperoxidase (MPO)-antineutrophil cytoplasmic antibodies (ANCA)-positive patients, whereas the remaining 6 MPO-ANCA-negative patients showed eosinophilic vasculitis in 3 and a mixed infiltrate of neutrophils and eosinophils in another 3 patients. Five patients with muscular vessel vasculitis showed vasculitis at different inflammatory stages in separate or coexisting at the same biopsied skin lesions: acute stage (eosinophilic vasculitis), granulomatous stage (granulomatous vasculitis), and healed stage. Coexistent small vessel and muscular vessel vasculitis was found in 4 patients., Conclusions: The histopathologic spectrum of dermal small vessel vasculitis in EGPA ranges from eosinophilic vasculitis with negative MPO-ANCA at one end to neutrophilic vasculitis with positive MPO-ANCA at the other end. The affected vessels ranging from dermal small vessels to subcutaneous muscular vessels in addition to the MPO-ANCA phenotype may account for the many facets of vasculitis in EGPA.

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., (Copyright © 2010 John Wiley & Sons A/S.)

Background: Although granulomatous arteritis is usually found in extracutaneous Churg-Strauss syndrome (CSS) lesions, the vasculitis in CSS cutaneous lesions typically shows small vessel vasculitis (leukocytoclastic vasculitis) without demonstrating the feature of granulomatous arteritis confirming the proper classification of CSS in the category of granulomatous vasculitis., Methods: Four deep excisional biopsies were obtained from three untreated CSS patients who presented with livedo reticularis and subcutaneous nodules. Tissue blocks were recut and submitted for hematoxylin and eosin and elastic tissue staining to evaluate the histological features of the affected vessels. Immunostaining for histiocytes, lymphocytes, and neutrophils were performed on serial sections to confirm the cellular infiltration., Results: In all specimens, subcutaneous granulomatous arteritis was observed. The unique histological feature distinct from other vasculitic disorders is characterized by marked infiltration of histiocytes and multinucleated giant cells in and around the disrupted subcutaneous arterial walls mixed with an eosinophilic infiltrate. In two specimens, granulomatous arteritis was found in the subsequent serial sections, not in the initial sections. The initial section may show extravascular granulomatous inflammation without evidence of vasculitis., Conclusions: Granulomatous arteritis as identified in the extracutaneous lesions can also be found in subcutaneous CSS lesions presenting with livedo reticularis and/or subcutaneous nodules.