Eosinophilia in Microscopic Polyangiitis: A Rare Case Report and Review of Literature

Aim and background: Microscopic polyangiitis (MPA) is a rare ANCA-associated vasculitis (AAV) causing necrotizing small-vessel vasculitis.Unlike other AAV subtypes, MPA is not associated with eosinophilia.Here, we report the 1st case of MPA with eosinophilia.Case description: A 70-year-old female presented with hemoptysis, significant weight loss, anorexia, and dyspnea.Her hematologic and radiological investigations revealed severe anemia with eosinophilia and altered renal functions without any renal symptoms.Her CT chest showed air space opacification, ground glass haziness, interstitial thickening, and bronchiectatic changes.Her positive MPO-ANCA and hemosiderin-laden macrophages in bronchoscopy-guided transbronchial lung biopsy confirmed the diagnosis of MPA.On follow-up, the patient had improved clinically and radiologically.Conclusion: MPA can rarely be associated with eosinophilia.Serological and histopathological confirmation is required for the diagnosis of MPA.Clinical significance: As per diagnostic criteria for MPA, eosinophilia helps to exclude MPA, but rarely, a patient may present with eosinophilia.In tuberculosis (TB) endemic countries, TB should be ruled out due to the overlapping clinical presentation.