Additional studies of this patient group revealed that serum levels of IP-10 in the SSc-PAH patients correlated with pulmonary vascular resistance, and levels of brain natriuretic peptide in serum, and serum IP-10 levels in the SSc-PAH patients inversely correlated with cardiac index and 6-min walks test (117). The gene discussed is NPPB; the disease is systemic sclerosis.