Nonspecific interstitial pneumonia preceding diagnosis of collagen vascular disease

Background The aim of this study was to evaluate the incidence and clinical features of patients who developed collagen vascular disease (CVD) after an initial diagnosis of idiopathic nonspecific interstitial pneumonia (NSIP). Methods We conducted a retrospective review of 72 consecutive patients with NSIP who were diagnosed by surgical lung biopsy in our institution (idiopathic NSIP, n = 35; CVD-NSIP, n = 37 at initial diagnosis). No patients fulfilled the American College of Rheumatology criteria for a diagnosis with CVD within six months after the diagnosis of idiopathic NSIP. Results Of 35 patients initially diagnosed with idiopathic NSIP, six patients (17.1%) developed CVD during the follow-up period (5.5 ± 5.0 years); three patients were diagnosed with dermatomyositis (DM), two patients with overlap syndrome (DM and Sjogren's syndrome), and one patient with rheumatoid arthritis. The mean time until CVD diagnosis was 2.0 years (six months - 3.5 years), and the one-, two- and three-year incidences of CVD development were 3.6%, 15.2% and 20.0%, respectively. There was no significant difference in clinical characteristics and survival among patients with NSIP preceding CVD diagnosis, those with idiopathic NSIP, or those with CVD-NSIP. In addition, at the time of initial diagnosis, there was no significant difference for the fulfillment of previous criteria such as interstitial pneumonia with autoimmune feature (IPAF) between patients with NSIP preceding CVD diagnosis and those with idiopathic NSIP. Conclusions It is difficult to predict CVD occurrence and careful attention is needed to detect the development of CVD in patients with idiopathic NSIP.