Background:no previous study has been done about if the connective tissue diseases (CTDs)-associated pulmonary artery hypertension (CTD-APAH) has different phenotypes among different CTDs.This study was designed to compare the hemodynamic,echocardiographic characteristics and their reaction to inhaled iloprost between systemic lupus erythematosus (SLE)-associated PAH (SLE-APAH) and PAH associated with systemic sclerosis (SSC-APAH).