The overlap is due to the combination of peripheral eosinophilia (≥ 1 × 109/mcl) and necrotizing pulmonary granulomas associated with an eosinophilic infiltration (which favored EGPA), elevated serum PR3-ANCA levels and ENT involvement with nasal obstruction and saddle nose, which are much more commonly seen in patients with GPA. This evidence concerns the gene PRTN3 and granulomatosis with polyangiitis.