Clinical features of microscopic polyangiitis with usual interstitial pneumonia-like fibrosis in comparison with idiopathic pulmonary fibrosis

Introduction Microscopic polyangiitis (MPA) patients presented with usual interstitial pneumonia (UIP) pattern are likely misdiagnosed as idiopathic pulmonary fibrosis (IPF). Aims To explore the clinical features of MPA with UIP-like and the difference between MPA and IPF. Methods The study population was composed of 36 patients diagnosed as MPA with UIP-like pattern on chest HRCT (MPA/UIP) in Beijing Chao-Yang Hospital of Capital Medical University from Aug. 2003 to Aug. 2013 (male/female ratio, 1.77:1, age 67.25±11.50 years). 72 patients with IPF (male/female ratio, 3.5:1, age 63.96±10.00 years) admitted in the same time were analyzed. Results Many non-specific inflammatory markers such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), immunoglobulin G, ferritin and peripheral white blood cell count, neutrophilic granulocyte percent, fibrinogen, D-dimer were increased in MPA/UIP patients ( P l0.05). Besides positive ANCA, rheumatoid factor (RF) was mostly positive in MPA/UIP patients (11/28 vs 5/52, P =0.002). Abnormal blood urea nitrogen and serum creatinine, mild anemia and hypoproteinemia and hematuria and/or proteinuria were more common in MPA/UIP patients( P l0.05). However, serum carcinoembryonic antigen and CA199 were higher in IPF patients(Pl0.05). Conclusions MPA patients with UIP-like pattern have abnormality of more laboratory examinations and can be differentiated with IPF by comprehensive analysis of clinical and laboratory findings.