Interstitial lung disease and anti-myeloperoxidase antibodies: not a simple association

Anti-neutrophil cytoplasmic antibodies (ANCA), mainly anti-myeloperoxidase (MPO) 29 antibodies, have been frequently identified in patients with idiopathic pulmonary fibrosis (IPF). 30 However, their role remains unclear and only 7-23% of these patients develops clinically overt vas- 31 culitis. We aimed to investigate the clinical, serological and radiological features, and prognosis of 32 anti-MPO-positive interstitial lung disease (ILD) patients. 33 Fifty-eight consecutive patients firstly referred for idiopathic interstitial pneumonia and showing 34 serological positivity of anti-MPO antibodies were retrospectively enrolled. For each patient, clini- 35 cal data, lung function testing, chest high resolution computed tomography (HRCT) pattern, and 36 survival were recorded. 37 Thirteen patients developed a rheumatic disease during a median follow-up of 39 months. Usual 38 interstitial pneumonia (UIP) was the most frequent ILD pattern, significantly influencing the pa- 39 tients’ survival. In fact, while the 52-week survival of the overall population was 71.4%±7.5, signif- 40 icantly higher than IPF, survivals of anti-MPO patients with UIP pattern and IPF were similar. 41 Forced vital capacity and diffusion lung capacity for CO significantly declined in 37.7% and 41.5% 42 of cases, respectively, while disease progression at chest HRCT was observed in 45.2%. 43 A careful clinical history and evaluation should be always performed in ILD patients with anti- 44 MPO antibodies to early identify patients developing a systemic rheumatic disease.