Idiopathic pulmonary arterial hypertension and pulmonary veno-occlusive disease: similarities and differences.

Pulmonary veno-occlusive disease (PVOD) is a rare disorder and can be misdiagnosed as idiopathic pulmonary arterial hypertension (iPAH). PVOD and iPAH often share a similar clinical presentation, genetic background, and hemodynamic profile. PVOD accounts for 5 to 10% of cases initially considered as iPAH. When compared with iPAH, PVOD is characterized by a higher male:female ratio, higher tobacco exposure, and lower PaO (2) at rest, diffusing capacity for carbon monoxide (DLCO), and oxygen saturation nadir during the 6-minute walk test. High-resolution computed tomography (HRCT) of the chest may be suggestive of PVOD in the presence of centrilobular ground-glass opacities, septal lines, and lymph node enlargement. Additionally, occult alveolar hemorrhage is associated with PVOD. Definitive diagnosis necessitates a surgical lung biopsy; however, this procedure is exceedingly high risk in this patient population and is generally not recommended. Therefore, a noninvasive diagnostic approach using HRCT of the chest, arterial blood gases, pulmonary function tests, and bronchoalveolar lavage may be helpful to detect PVOD. In contrast with iPAH, PVOD is characterized by an even poorer prognosis and the possibility of developing severe pulmonary edema with specific PAH therapy. Lung transplantation remains the treatment of choice, but cautious use of specific PAH therapy can be helpful in select patients while awaiting this intervention.