Prevalence and outcome of pulmonary fibrosis in microscopic polyangiitis

We sought to determine the type of pulmonary involvement in microscopic polyangiitis (MPA), primarily focusing on pulmonary fibrosis (PF), its prevalence, temporal relationship with other disease manifestations and outcome. 33 patients (16 males) with biopsy proven perinuclear anti-neutrophilic cytoplasmic antibody-positive MPA (age 63.5 yrs) participated in the study. Pulmonary involvement was assessed using standard methods, including radiographic imaging (chest radiographs and high-resolution computed tomography), pulmonary function testing, bronchoscopy and bronchoalveolar lavage, and, if indicated, lung biopsy. All-cause mortality was analysed by the Kaplan-Meier method and was compared between MPA patients with and without PF. At the time of diagnosis, renal involvement was detected in all patients, with renal biopsies being consistent with segmental necrotising glomerulonephritis in all patients. The most common respiratory symptom was haemoptysis, which was found in nine (27%) patients. PF was present in 12 (36%) patients at the time of diagnosis, whereas one patient developed PF while on therapy approximately 10 yrs after disease diagnosis. In seven patients with PF, respiratory symptoms related to fibrosis preceded other disease manifestations by a median (range) period of 13 (5-120) months. Patients were followed up for a period of 38+/-30 months. Presence of PF was associated with increased mortality (p = 0.02), with six deaths occurring in the fibrotic group and one in the nonfibrotic group. In the fibrotic group most deaths were related to PF. PF occurs frequently in MPA, may precede other disease manifestations by a variable length of time and has a poor prognosis.