Hypertensive pulmonary vascular disease associated with patent ductus arteriosus. Primary or secondary?

In an infant with patent ductus arteriosus and pulmonary hypertension, elevated pulmonary vascular resistance persisted following ligation of the ductus. Histologic examination of a pulmonary biopsy at two years of age and tissue obtained at autopsy at three years of age showed obstructive pulmonary vascular disease. The question as to whether the organic vascular lesions are secondary to the effects of the patent ductus or part of pulmonary hypertension cannot be resolved. The age of the patient favors a primary etiology.