Microscopic polyangiitis hiding behind the mask of COVID-19: A case series and minireview

Abstract

Microscopic polyangiitis (MPA) is one of the three clinical phenotypes of vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA). Although MPA is considered a rare form of ANCA-associated vasculitis (AAV), clinical evidence shows that it is fairly common among nephrologists, as it manifests as a systemic, weak-immune vasculitis affecting glomerular capillaries, resulting in necrotizing glomerulonephritis (GN) diagnosed in nearly 100% of MPA patients. The issue of AAV in general, and MPA specifically, has gained significant importance in the context of the ongoing SARS-CoV-2 coronavirus pandemic, as both conditions share common anatomical sites of infection and inflammation. This study presents three new cases of MPA in post-COVID-19 patients. The analysis and presentation encompassed demographic data, patient history regarding comorbidities, details of follow-up care, chronology with COVID-19, and laboratory findings at the time of MPA diagnosis. A comparative analysis of the chronological progression of MPA in the documented clinical cases reveals the polymorphic nature of early-stage clinical manifestations, as well as diverse patterns of disease progression in the advanced stage. Additionally, we provide a brief literature review on diagnostic challenges, pathogenetic mechanisms underlying the relationship between SARS-CoV-2 and AAV, and peculiarities of clinical presentations in early and advanced stages of MPA.