Microscopic polyangiitis associated with pulmonary fibrosis

Microscopic polyangiitis (MPA) is a systemic necrotizing vasculitis characterised by inflammation of the small blood vessels, the absence of granulommas on histopathological specimens, with few or no immune deposits and the presence of circulating anti-neutrophil cytoplasmic antibodies (ANCAs). The classic pulmonary manifestation is diffuse alveolar haemorrhage (DAH), but its association with pulmonary fibrosis (PF) has been increasingly reported and may be the first manifestation of MPA. Our aim was to evaluate MPA patients with PF and compare their characteristics and evolution to those of MPA patients without PF. We conducted a retrospective review of MPA patients followed in our hospital over a 15-year period. They were divided into two subgroups, with PF (MPA-PF) and without PF (MPA-non PF), and their clinical and functional features were compared. Nine of the 28 patients were classified as MPA-PF (32%). This subgroup showed significantly more respiratory symptoms and higher mortality than MPA-non PF subgroup. The most frequent chest computed tomographic pattern of PF was usual interstitial pneumonia. PF preceded other manifestations of vasculitis in five patients and occurred simultaneously in the remaining four. During the follow-up period, four deaths were reported in the MPA-PF subgroup. No deaths were registered in the MPA-non PF subgroup. We found a high prevalence of MPA-PF patients (32%), most of whom had a poor outcome and PF was often the first manifestation of the disease.