 Sickle cell disease SCD affects 250,000 births per year worldwide, with 70-80,000 patients currently residing in the US. Although classically thought of as a genetic hemoglobinopathy, most of the clinical complications are vascular in etiology and pulmonary manifestations are the primary cause of morbidity and mortality. Pulmonary hypertension PH, one such pulmonary complication, occurs in 6-10.5 of SCD adults and is associated with a 60 four-year survival 1-4. No specific therapy for PH in SCD exists representing an area of intense clinical need in this field. 