Exhaled Nitric Oxide Levels in Systemic Sclerosis With and Without Pulmonary Involvement*

Background: Systemic sclerosis (SSc) is a connective tissue disorder of unknown etiology that is often complicated by pulmonary involvement, with pulmonary hypertension (PH) and interstitial lung disease (ILD) being the major causes of death. It has been suggested that the amount of nitric oxide (NO) in exhaled air may predict the onset of complications. The aim of the study was to measure exhaled NO in SSc patients and investigate its relationship with pulmonary involve-ment with and without PH. Methods: Fifty patients (5 men and 45 women; mean age, 59.1 11.7 years [ SD]) with a diagnosis of SSc based on the preliminary criteria of the American Rheumatism Association, and 40 healthy control subjects (5 men and 35 women; mean age, 58.3 12.2 years) underwent exhaled NO measurements by means of a chemiluminescence analyzer, pulmonary function tests, high-resolution thorax CT, and Doppler echocardiography. Results: Exhaled NO concentrations were significantly higher in SSc patients than control subjects (p 0.02), and significantly lower in the patients with ILD and/or PH than in those without PH (p < 0.01). There was a significant inverse correlation between pulmonary artery systolic pressure and exhaled NO concentration in all of the studied patients (r 0.5, p < 0.001)