Additional Study Information: Systemic sclerosis (SSc) is a systemic connective tissue disease characterized by fibrosis and atrophy, namely of the skin, internal organs, joints, and skeletal muscles. There are numerous manifestations of SSc that affect multiple organ systems. The major pulmonary manifestations of SSc, interstitial lung disease and systemic sclerosis-associated pulmonary arterial hypertension (SSc-PAH), produce common and serious complications. Rheumatologists and cardiologists at Columbia University are conducting a research study to evaluate the safety and tolerability of a medication for scleroderma-associated pulmonary arterial hypertension. The study involves: Two infusions of the medication and clinical assessments to evaluate the safety and efficacy of the drug. Your participation may help patients with scleroderma and pulmonary arterial hypertension like you receive improved therapies in the future.