Overview of Lung Involvement

In systemic sclerosis (SSc), interstitial lung disease (SSc-ILD) is a major cause of morbidity and mortality in SSc with pulmonary hypertension a frequent complication. Although a rare disease in the general community, SSc-ILD is important and significantly prevalent in respiratory and rheumatologic practice, especially at referral centres. Nonspecific interstitial pneumonia, most commonly fibrotic, is much the most frequent histologic pattern. High-resolution computed tomography (HRCT) is the reference test in the identification of SSc-ILD. Key risk factors for ILD in SSc include the presence of diffuse cutaneous disease and, more importantly, anti-topoisomerase I (anti Scl-70) antibody positivity. In clinical practice, the distinction between ‘pre-clinical’ limited abnormalities on HRCT and clinically significant ILD is a key consideration. In isolation, the severity of exertional dyspnoea is often misleading: symptoms should be integrated with pulmonary function tests and the extent of disease on HRCT. The pattern of pulmonary function impairment is a useful adjunct to echocardiography in identifying pulmonary hypertension. The detection of serial change in SSc-ILD severity requires the integration of symptomatic and pulmonary function trends with the addition of serial HRCT in selected cases. The severity of disease, ongoing disease progression and a short duration of systemic disease are key factors in reducing the threshold for immediate intervention. Until recently, SSc-ILD treatment has been confined to suppression of pulmonary inflammation, most commonly with cyclophosphamide or mycophenolate mofetil. Tocilizumab and rituximab have now been validated as second-line treatments, and anti-fibrotic therapy, especially nintedanib, represents the most striking recent treatment advance.