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.
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