Recurrence of Pulmonary Hypertension After Unilateral Lung Transplantation: Histological Evidence of Vasoconstrictive Mechanism

Pulmonary hypertension (PH) is widely recognized as a disease driven by both vasoconstriction and vascular remodeling. Vasoconstriction is thought to play a predominant role in the early stages of PH, whereas the contribution of vascular remodeling increases as the disease progresses. However, clinical or histological evidence of this pathological progression has not been reported. We describe a case of recurrent PH after unilateral right lung transplantation, ultimately requiring bilateral transplantation 9 years later, and discuss the pathogenesis of PH based on histological findings in the transplanted normal lungs and changes in pulmonary blood flow observed by lung perfusion scintigraphy. Serial lung perfusion scintigraphy revealed a dynamic shift in pulmonary blood flow, initially favoring the transplanted lung, followed by a gradual decline. Histological examination demonstrated that the right lung of the second transplantation showed minimal vascular remodeling. These findings provide compelling evidence that vasoconstriction was the predominant contributor to PH after the first transplantation, offering unique insight into early PH pathobiology.