Endostatin has been found to inhibit pulmonary artery endothelial cell proliferation and migration, and promotes endothelial cell apoptosis, important features involved in PAH pathophysiology.37 These findings were confirmed in a study including two largely unselected cohorts, showing that endostatin levels were elevated in both patients with SSc and mixed connective tissue disease (MCTD).30 Furthermore, in this study elevated endostatin was associated with both scleroderma renal crisis and PAH in SSc. Here, COL18A1 is linked to mixed connective tissue disease.