B64-33 Pulmonary Veno-occlusive Disease: Unmasking the Risks of Standard Pulmonary Arterial Hypertension Therapy

Abstract Introduction Pulmonary veno-occlusive disease (PVOD) is a rare, aggressive form of pulmonary hypertension caused by fibrotic obstruction of small pulmonary veins and venules. Although it may mimic pulmonary arterial hypertension (PAH), PVOD differs in pathobiology, prognosis, and response to vasodilator therapy. Early recognition is crucial to prevent complications from standard PAH treatments. Case A 63-year-old woman with newly diagnosed pulmonary hypertension presented with progressively worsening dyspnea, classified as NYHA Class II. High-resolution CT revealed patchy ground-glass opacities, interlobular septal thickening, and mild mosaic perfusion, findings consistent with PVOD. Right heart catheterization showed mild pulmonary hypertension with a pulmonary artery pressure of 43/12/25 mmHg, a transpulmonary gradient of 11 mmHg, and pulmonary vascular resistance of 4 Wood units; mixed venous oxygen saturation was 61%. Pulmonary function testing demonstrated a mild restrictive ventilatory defect (slightly reduced FEV1, FVC, and TLC), a preserved FEV1/FVC ratio, and moderately reduced DLCO. An initial diagnosis of WHO Group 1 PAH was made, and vasodilator therapy was initiated. The patient’s respiratory symptoms worsened after starting sildenafil, consistent with the paradoxical hemodynamic response seen in PVOD. Upon discontinuation, she improved clinically, with stabilization of oxygen needs and partial resolution of pulmonary edema on chest radiography, further supporting PVOD and its distinct pathophysiologic response to vasodilators. Discussion PVOD is characterized by fibrotic intimal thickening and obliteration of small pulmonary veins and venules, causing elevated post-capillary pressure, capillary congestion, and right heart failure. Unlike PAH, PVOD involves venous remodeling and predisposes to pulmonary edema when vasodilators increase flow through obstructed venous outflow tracts. Characteristic HRCT findings include centrilobular ground-glass opacities, interlobular septal thickening, pleural effusions, and mediastinal lymphadenopathy. A markedly reduced DLCO (often 40% predicted) also favors PVOD over idiopathic PAH. Genetic predisposition occurs in familial disease with biallelic EIF2AK4 mutations, present in up to ∼25% of sporadic cases and associated with poorer prognosis. PVOD accounts for 3-12% of cases initially labeled idiopathic PAH. Standard PAH therapies (e.g., phosphodiesterase-5 inhibitors, endothelin receptor antagonists) can precipitate pulmonary edema, underscoring the need for diagnostic caution, comprehensive imaging, genetic evaluation, and referral to specialized pulmonary hypertension centers. Management is primarily supportive with oxygen, cautious diuresis, and right-ventricular support; lung transplantation remains the only curative option. Median survival without transplantation is typically 1-2 years. This abstract is funded by: None