Microscopic polyangiitis in a patient with preexistent pulmonary fibrosis by 8 years Case report and review of the literature

Microscopic polyangiitis (MPA) is a systemic necrotising vasculitis that affects the small-caliber blood vessels and a common cause of pulmonary-renal syndrome. We present a patient case with manifestations of rapidly progressive glomerulonephritis and alveolar hemorrhage along with positive perinuclear antineutrophil cytoplasmic autoantibodies (p-ANCA) against myeloperoxidase (MPO). The patient was diagnosed with pulmonary fibrosis (PF) based on the findings of his chest computed tomography 8 years ago. 6 months ago he demonstrated nephrotic syndrome, had a kidney biopsy with findings of focal segmental necrotizing glomerulonephritis with glomerular crescents and in the presence of positive MPO-ANCA was diagnosed with MPA and treated with cyclophosphamide and prednisolone with partial response. In his present hospitalization he was admitted with symptoms of respiratory tract infection, which was successfully treated with antibiotics. Upon its remission he underwent a bronchoscopy with bronchoalveolar lavage, which was compatible with alveolar hemorrhage (50% hemosiderin-laden macrophages). The coexistence of MPA and PF is presenting more often in recent studies, as a result of the most widespread use of the high resolution chest computed tomography. The majority of these patients have positive MPO-ANCA, clinically manifested PF at the time of vasculitis diagnosis, radiological and pathological pattern of usual interstitial pneumonia (UIP) and a worse prognosis than those without PF. The pathogenetic association between these two conditions is not clear and 3 hypothetic mechanisms have been proposed: evolvement of fibrosis as a result of either the repeated episodes of alveolar hemorrhage or the induced oxidative stress in the presence of anti-MPO antibodies or reversely production of ANCA as a result of the fibrotic inflammatory process.