Lung involvement in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, immune system activation, and fibrosis of the skin and internal organs [1]. While over the recent years, the prognosis of SSc patients has greatly improved, thanks to a better understanding of the underlying pathogenetic phenomena and the arousal of targeted therapies, the disease still presents the highest morbidity and mortality among all connective tissue diseases [2]. Compared to those years when SSc renal crisis represented the leading cause of death, now in the last decades, lung involvement (both pulmonary hypertension and pulmonary fibrosis) has become the primary cause of SSc-related death [3]. Therefore, clinicians involved in SSc care should be aware of the most recent evolutions in the field of SSc with particular attention to lung involvement. In fact, the early detection and the prompt treatment both of fibrotic and vascular lung disease may have fundamental impact on patients' quality of life and survival. In SSc, lung involvement is characterized by interstitial lung disease (ILD), which is due to the fibrosis of the alveolo-capillary membrane, and pulmonary arterial hypertension (PAH), which reflects the proliferative vasculopathy affecting pulmonary vessels [1,4,5]. Usually, SSc is classified according to 2013 ACR/EULAR criteria [6] and is also subsetted in a limited cutaneous (lcSSc; affecting the face, neck and distal limbs) and a diffuse cutaneous SSc (dcSSc; affecting the proximal limbs, abdomen, and chest). Both subsets are associated with specific clinical features and autoantibody positivity [7]. In this chapter, either SSc-ILD or SSc-PAH will be discussed, and, given the historical period, the clinical and prognostic data on COVID-19 in SSc patients will be also presented.