Characteristics and Prognosis of Microscopic Polyangiitis Patients with Diffuse Alveolar Hemorrhage and Interstitial Lung Disease

Objective To evaluate the clinical characteristics and prognostic predictors of patients with diffuse alveolar hemorrhage (DAH) and/or interstitial lung disease (ILD) secondary to microscopic polyangiitis (MPA) in a Chinese general hospital. Methods We retrospectively reviewed the medical records of MPA patients admitted to internal medicine departments between the year 2002 and 2012. The patients were divided into the ILD, DAH, DAH combined with ILD (DAHILD), and no pulmonary involvement (NPI) groups according to pulmonary involvement patterns. The clinical characteristics at diagnosis were analyzed. The risk factors associated with short-term death and long-term death were identified with Logistic regression and Cox analysis.Results Of 193 newly diagnosed MPA patients, 181 patients were enrolled in the research, of which 19 had DAH alone, 96 had ILD alone, 18 had DAH and DAH concurrently, and 48 had NPI. The median of serum creatine level in the DAH group was 449 μmol/L, significantly higher than that in the ILD group (123 μmol/L, Nemenyi = -35.215, P = 0.045) and DAHILD group (359 μmol/L, Nemenyi = -43.609, P = 0.007). The median follow-up time was 67 (range: 1-199) months. Patients in the ILD group were older than those in the DAH group (median: 69 years vs. 57 years, Nemenyi = 43.853, P= 0.005). The patients with both DAH and ILD had combined features of the two subtypes, and the highest mortality (72.2% at the end of follow-up). The elevated white blood cell count was a risk factor for short-term death (OR = 1.103, 95%CI: 1.008-1.207, P = 0.032 for one month; OR = 1.103, 95%CI: 1.026-1.186, P = 0.008 for one year). Old age (HR= 1.044, 95%CI: 1.023-1.066, P < 0.001), cardiovascular system involvement (HR = 2.093, 95%CI: 1.195-3.665, P = 0.010), poor renal function (HR = 1.001, 95%CI: 1.000-1.002, P = 0.032) were risk factors for long-term death. Pulmonary infections (38/54) were the leading causes of death, especially for the patients with ILD. Besides, 49 patients suffered from pulmonary infections in the first year after diagnosis. Conclusions MPA patients who presented with different pulmonary involvement patterns have completely different clinical features. These subtypes probably have different pathogenesis and should be studied separately.