Thank you for your question. Pulmonary hypertension can definitely be complicated, and can be due to a combination of causes. And while congenital heart defect is likely the biggest contributor, there have been reports of pulmonary hypertension in approximately 19 percent of cases of unilateral agenesis of the lung (though it is more common in agenesis with someone who also has a left-to-right shunt) (Capuani et al. 1982). And yes, restrictive lung disease can contribute to PH as well.