A63-04 Pulmonary Vascular Disease Without Pulmonary Hypertension: A Case of Pulmonary Capillary Hemangiomatosis/Pulmonary Veno-Occlusive Disease Presenting With Isolated Diffusion Impairment

Abstract Introduction Pulmonary capillary hemangiomatosis (PCH) / pulmonary veno-occlusive disease (PVOD) comprise 5-10% of idiopathic pulmonary arterial hypertension (PAH) cases and classically present with worsening hypoxemia due to pulmonary edema after initiation of pulmonary vasodilators. Given the limited efficacy of pulmonary vasodilators in this condition, recognition of PCH/PVOD should prompt early referral for lung transplant. We present a patient with PCH/PVOD notable for diminished DLCO and hypoxemia preceding hemodynamic changes diagnostic of pulmonary hypertension. Case Description A 53-year-old woman with mild OSA and ADHD was referred for evaluation of hypoxemia, which had progressed from mild exertional hypoxemia to continuous 3L/min oxygen requirement over a two-year period. At initial visit in March 2022, her DLCO was 67% predicted with otherwise normal spirometry and lung volumes, and she had unremarkable transthoracic echocardiography and CT chest findings. Exercise right heart catheterization (RHC) demonstrated a resting mPAP of 14 mmHg and PVR of 1.81 WU. The rest-to-exercise mPAP/ CO slope was 2.05 mmHg/L/min, suggesting a normal pulmonary vascular response to exercise. The patient’s hypoxia progressed in the following two years until she required 5L/min, at which time extensive cardiac shunt evaluation was negative. Repeat RHC at that time in April 2024 revealed elevated mPAP of 27 mmHg, PVR of 3.3 WU, and diastolic pulmonary gradient of 3, without vasodilator response. DLCO had further decreased to 37% predicted. In December 2024 her pre-capillary pulmonary hypertension worsened on RHC with increased PVR to 6.5 WU and mPAP to 38 mmHg, prompting initiation of vasodilators. Her oxygen requirements escalated in the 2 weeks after initiation with significant exertional desaturation on 8 L/min. She underwent expedited bilateral orthotopic lung transplantation, and explanted tissue revealed diffuse thickening of alveolar septa with increased capillary-sized vascular spaces as well as areas of venous occlusion, consistent with PCH/PVOD (Figure 1). Discussion PCH and PVOD exist along a spectrum of pulmonary vascular disease with overlapping clinical features, histopathology, and genetic underpinnings. PCH/PVOD carries a poor prognosis and can progress rapidly. Early identification or high clinical suspicion for PCH/PVOD is an indication for transplant evaluation per 2024 ISHLT consensus guidelines. Our case contributes to limited literature highlighting the natural history of the disease, which may include dyspnea, hypoxia, and diminished DLCO preceding hemodynamic changes. Awareness of this disease entity during the evaluation of patients with occult hypoxemia may facilitate evaluation, or even serial evaluations, for pulmonary vascular disease and thus maximize treatment options. This abstract is funded by: None