Mild pulmonary hypertension is not uncommon in the setting of sickle cell disease and may be present in up to two thirds of patients, along with left atrial and left ventricular dilatation. In fact, pulmonary hypertension may be related to elevated left-sided filling pressures or a high output state from anemia. Although Kaur and colleagues did not give the individual data for the four patients with sickle cell disease, such as the mean pulmonary artery pressure, pulmonary capillary wedge pressure, and cardiac output, we are given the pulmonary resistance. Of note, the pulmonary vascular resistance in these four patients is markedly lower than that in patients with other forms of secondary pulmonary hypertension, as reported in our study. The mean pulmonary vascular resistance in their case series is 3.13 units, while in our patients it was 14.4 units. It would be difficult to justify the use of such a complicated therapy as long-term prostacyclin infusion in patients with mild pulmonary vascular disease. Certainly, a better understanding of the mechanism of pulmonary vascular disease in the setting of sickle cell disease would aid in the treatment of this serious disorder.