other forms of ph are far more common. in systemic scleroderma, the incidence has been estimated to be 8 to 12% of all patients; in rheumatoid arthritis it is rare. however, in systemic lupus erythematosus it is 4 to 14%, and in sickle cell disease, it ranges from 20 to 40%. up to 4% of people who suffer a pulmonary embolism go on to develop chronic thromboembolic disease including pulmonary hypertension. a small percentage of patients with copd develop pulmonary hypertension with no other disease to explain the high pressure. on the other hand, obesity-hypoventilation syndrome is very commonly associated with right heart failure due to pulmonary hypertension.