Systemic sclerosis, also called scleroderma, progressive systemic sclerosis, or CREST syndrome, is a rare autoimmune connective tissue disease with fibrosis and vasculopathy. Patients often have sclerotic, thickened skin, but some experience significant organ damage. Immunosuppressive therapy is a common approach to patients with systemic sclerosis, but there is a subset of patients that do not respond well to treatment.