Microscopic polyangiitis: Diagnostic challenges and pulmonary manifestations: A case study

Microscopic polyangiitis (MPA) is a systemic necrotizing vasculitis that primarily affects small-caliber vessels. Previous studies have reported a pulmonary involvement frequency of 22% to 29%. Glomerulonephritis and alveolar hemorrhage are common features. It is usually associated with anti-neutrophil cytoplasmic antibodies (ANCA) directed against myeloperoxidase (MPO), which are considered pathogenic. The presence of positive p-ANCA is a guiding element in the diagnosis of MPA. We provide a detailed description of the clinical manifestations, diagnostic approach, and treatment of MPA in a 62-year-old man who presented with alveolar hemorrhage but no renal involvement. The treatment included the use of high-dose corticosteroids to suppress the autoimmune response. Life-threatening or organ-threatening diseases are treated with glucocorticoids and cyclophosphamide (in bolus). If renal function is preserved, methotrexate may be considered to induce remission, and maintenance therapy is recommended with azathioprine, while mycophenolate mofetil can be used as a second-line medication.