Systemic sclerosis (SSc, AKA scleroderma) is an autoimmune condition characterized by endothelial damage and progressive fibrosis of the skin and internal organs. One of the leading causes of morbidity and mortality in patients with SSc is pulmonary hypertension (PH), which is estimated to occur in up to 31% of high risk SSc patients. Early detection of patients with SSc-PH may lead to improved outcomes and although there have been concerted efforts to accurately screen for SSc-PH, these patients continue to present with advanced disease and suffer from poor survival. Therefore, better methods to screen for patients with PH and, perhaps more importantly, to screen for those at risk for PH development are desperately needed. Since PH and SSc are disorders originating from the endothelium, biomarkers that reflect endothelial damage are very promising tools to identify early disease. Such potential biomarkers include endothelial microparticles, asymmetric dimethylarginine (ADMA), pentraxin-3, and soluble endoglin. No previous study has used a combination of these biomarkers to detect the presence of PH in patients with SSc, or studied the novel concept of exercise-induced changes in biomarker levels. The investigators will collect the above listed endothelial biomarkers before and after exercise, and combine these levels with exercise echocardiogram findings, and routine clinical information to derive a composite detection score for the early identification of systemic sclerosis-associated PH.

Inclusion Criteria:

• 1. Age >18 years 2. Meet American College of Rheumatology criteria for SSc

Exclusion Criteria:

1. Chronic kidney disease (estimated creatinine clearance <50mL/min)
2. Uncontrolled hypertension (diastolic blood pressure>120mmHg)
3. Acute coronary syndrome within the past 6 months
4. Chronic obstructive pulmonary disease
5. Diabetes mellitus
6. Hemolytic anemia
7. Active tobacco abuse

The study population will consist of 26 patients with systemic sclerosis-associated pulmonary hypertension and 26 patients with systemic sclerosis but no diagnosis of current pulmonary hypertension.