2. Current diagnosis of PH associated with an acceptable etiology as outlined in the protocol, including: PH due to the following etiologies: 1) PAH including idiopathic and familial PAH and PAH associated with collagen vascular disease, congenital systemic-to-pulmonary shunts (including Eisenmenger's syndrome), human immunodeficiency virus (HIV) infection, drugs and toxins, thyroid disorders, glycogen storage disease, Gaucher disease, hemoglobinopathies, and splenectomy (WHO Group 1); 2) PH associated with lung diseases and/or hypoxemia, including chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), sleep-disordered breathing, and alveolar hypoventilation disorders (WHO Group 3); 3) PH due to proximal or distal chronic thromboembolic obstruction (WHO Group 4); and 4) PH due to sarcoidosis (WHO Group 5).