Campo et al then focus their discussion on the threshold of the diffusion capacity of carbon monoxide (Dlco) (35% of predicted value) that we have found to be an independent risk of death in our population of patients with PAH-SSc (hazard ratio, 2.587; 95% CI, 1.029–6.501; P = .04). Obviously, Dlco may be reduced not only because of pulmonary vascular disease but also because of comorbid interstitial lung disease (ILD), which is not uncommon in such patients. Distinguishing pure PAH from pulmonary hypertension (PH) due to hypoxia associated with lung fibrosis in patients with SSc may be challenging, and both conditions are sometimes associated. Patients with evidence of ILD, as demonstrated by abnormal high-resolution CT scans of the chest and total lung capacity (TLC) ranging from 60% to 70% with elevated mean pulmonary arterial pressure >25 mm Hg at rest, were kept in the analysis set in case of the absence of extensive ILD or severe lung fibrosis, based on the expertise of our team, because they were considered more likely to have PAH-SSc rather than ILD-associated PH. We agree that such patients may be difficult to classify and that some may have quite severe ILD, which could contribute to PH. In order to address this comment, we have reanalyzed our data after exclusion of all patients with a TLC<70% and found a 40% cutoff of predicted Dlco value to be an independent risk of death at 3 years in patients with PAH-SSc (hazard ratio, 11.25; 95% CI, 1.38-91.60; P = .02). These consistent results suggest that Dlco is likely to be an important and relevant prognosis factor in patients with PAH-SSc. ILD, PH due to ILD, and PAH are not the sole causes of Dlco impairment in patients with SSc. Nevertheless, for clinical practice, it seems important to highlight the fact that a markedly impaired Dlco<35% to 40% of predicted value in patients with PAH-SSc may be associated with a worst-outcome scenario.