New-onset microscopic polyangiitis temporally associated with severe COVID-19 infection: A case report.

The coronavirus disease 2019 has been demonstrated to be a trigger for multiple immune-mediated diseases, such as antineutrophil cytoplasmic antibody-associated vasculitis. Associated vasculitis consists of rare autoimmune disorders that predominantly affect small vessels, leading to endothelial injury and tissue damage. We present a case of a newly diagnosed microscopic polyangiitis temporally associated with coronavirus disease 2019 infection in a previously healthy woman and a literature review. A 66-year-old female presented to the Emergency Room with fever, edema on her legs, productive cough, dyspnea, and hemoptysis. A chest computerized tomography scan revealed bilateral diffuse alveolar opacities with the appearance of diffuse alveolar hemorrhage. Blood analysis revealed a moderate normocytic, normochromic anemia with a hemoglobin of 6.6 g/dL, platelet count of 347 k/dL, leucocytes of 12,000/dL, a creatinine of 3.91 mg/dL (basal Cr: 0.9 mg/dL), and a Blood Urine Nnitrogen of 78 mg/dL. A urine sediment demonstrated glomerular hematuria, with mixed shapes of red blood cells. She was admitted to the intensive care unit and a bedside bronchoscopy revealed progressive bleeding with a bronchioalveolar lavage positive for diffuse alveolar hemorrhage. Given the critical involvement of the lungs and kidney function, the diagnostic approach revealed a positive p-anti-neutrophil cytoplasmic antibody on immunofluorescence and an anti-MPO (myeloperoxidase) level of 124.6 IU/mL. A renal biopsy demonstrated pauciimmune focal and segmental glomerulosclerosis. A diagnosis of microscopic polyangiitis triggered by severe acute respiratory syndrome coronavirus 2 infection was made, and immediate treatment with pulse-dose steroids and cyclophosphamide was initiated. The patient needed renal replacement therapy and was discharged for follow-up with nephrology and rheumatology services. The diagnostic approach of associated vasculitis can be more challenging in the coronavirus disease era. Atypical features in the pulmonary imaging and a rapid deterioration of the renal function should arise the clinical suspicion of the presence of an added condition to the coronavirus disease infection. Autoimmune conditions such as associated vasculitis should be evaluated even in the absence of previous autoimmune history. Prompt diagnosis and treatments must be prioritized to avoid end-organ definite damage. Further, larger and more collaborative studies are needed to confirm the potential role of coronavirus disease 2019 as a trigger of associated vasculitis.