Eosinophilic granulomatosis with polyangiitis (Churg-Strauss Syndrome) with microscopic eosinophilic thromboembolism and cardiac involvement: report of two cases
Eosinophilic granulomatosis with polyangiitis (EGPA) is a multisystem vasculitis of small- and medium-sized vessels and approximately 40% of patients with EGPA have circulating anti-neutrophil cytoplasmic antibodies (ANCAs). Recent studies have demonstrated that ANCA-negative EGPA patients have cardiac involvement and tissue eosinophilic infiltration more frequently than ANCA-positive patients. However, a causative relationship between cardiac involvement and tissue eosinophilic infiltration remains to be elucidated. Here we report two cases of ANCA-negative EGPA with microscopic eosinophilic thromboembolism as well as cardiac impairment. Although the cutaneous manifestations of the two cases were quite different, skin specimens from both patients demonstrated that the vessels in the mid- to deep dermis were occluded with fibrin materials and surrounded by marked eosinophilic infiltration without overt leukocytoclastic vasculitis or extravascular necrotizing granuloma. The thrombogenic potential of the eosinophil was revealed by the strong expression of major basic protein, which is thought to be involved in the inhibition of natural anti-coagulation activity and activation of platelets, in the walls of the occluded vessels. The implication of microscopic eosinophilic thromboembolism in EGPA without vasculitic or granulomatous lesions is discussed.