Microscopic Polyangiitis in a Patient with Diffuse Alveolar Hemorrhage and No Biochemical Renal Impairment

Microscopic polyangiitis (MPA) is an autoimmune disease characterized by inflammation of the small vessels and the presence of circulating anti-neutrophil cytoplasmic antibodies (ANCA). Resulting from an injury orchestrated by ANCA, MPA usually manifests as necrotizing glomerulonephritis (GN) and necrotizing pulmonary capillaritis. The major clinical feature of MPA is rapidly progressive GN; however, diffuse alveolar hemorrhage (DAH) that originates from pulmonary capillaritis is often the main reason for hospitalization. The clinical presentation of DAH is highly variable, ranging from asymptomatic radiographic abnormalities to fatal respiratory failure. Some patients may experience a variable degree of hemoptysis, accompanied by dyspnea, chest tightness and anemia. Early diagnosis and prompt therapy will lead to a good prognosis for patients with MPA. We describe a 44-year-old male with MPA presenting with hemoptysis for 1 month. DAH was detected by the presence of numerous hemosiderin-laden alveolar macrophages in bronchoalveolar lavage. The renal function at diagnosis was normal though microscopic hematuria was observed. The patient was successfully treated with rituximab, a monoclonal chimeric antibody targeting CD20, a cellsurface protein expressed on B-lymphocytes.