Pulmonary veno-occlusive disease masquerading as chronic thrombo embolic pulmonary hypertension

Pulmonary veno-occlusive disease (PVOD) is a rare cause of Group 1 Pulmonary Hypertension (PH) characterized by preferential remodeling of the pulmonary venules. Due to its aggressive course, the hemodynamic similarities to pulmonary arterial hypertension (PAH), this disease presents a diagnostic and therapeutic challenge. Case report: A 23 years old otherwise healthy Caucasian male smoker presented with 4 months of progressive exertional dyspnea, dry cough and weight loss without fever or hemoptysis. He underwent CT angiography (CTa) which showed no pulmonary embolism (PE) but showed ground glass opacities in his left upper lobe as well as diffuse hilar and mediastinal lymphadenopathy (MLAD) and enlarged pulmonary artery (PA). Arterial blood gas showed PO2 of 58 mmHg on room air, a restrictive pattern on PFTs, a reduced DLCO of 38%. An echocardiogram demonstrated normal ejection fraction with high PA pressure. An extensive workup to rule out a systemic disease was negative. Ventilation/perfusion (VQ) scan was done to rule out chronic thromboembolic pulmonary hypertension (CTEPH), demonstrated multiple bilateral perfusion defects in the right more than the left lung and thus was interpreted as high probability for PE. Due to weight loss he underwent biopsies of his MLAD which were found to be reactive. Patient was started on anticoagulation and planned for right heart catheterization (RHC) with pulmonary angiography (results are attached). The diagnosis of PVOD was favored and while undergoing evaluation for lung transplantation, he developed worsening hypoxia and refractory flash pulmonary edema with a trial of vasodilator therapy. Veno-Arterial Extra Corporal Membranous Oxygenation was used as a bridge for bilateral lung transplantation which he successfully underwent. The pathology of his explanted lungs confirmed the diagnosis of PVOD. Discussion: The annual incidence of PVOD is 0.1-0.2 cases per million/year. We suspected the diagnosis due to the hemodynamic features of high mean PA pressure with normal PCWP and very low RA pressure in light of the CT chest findings and reactive MLAD. The diagnostic dilemma involved the conflicting data between the VQ scan, (CTa) and RHC findings which were suggestive of CTEPH. As Recent studies discovered genetic causes for hereditary cases of PVOD, a new understanding of its pathogenesis may open the door for new medical treatments. The mortality rate is around 75% in the first year into diagnosis, lung transplantation remains the only curable option for eligible candidates