IL5 and eosinophilic granulomatosis with polyangiitis: Although EGPA is a hypereosinophilic disease, with elevated levels of IL-5 and eosinophils observed on biopsy of perivascular and vascular lesions [86], the relevance of these findings for overall disease pathogenesis was not previously known given the observed involvement of other immune pathways such as IL-17 and B-cells.