Pulmonary veno-occlusive disease: a clinical review

Pulmonary vasculopathy presents as a spectrum of diseases affecting the precapillary pulmonary arterioles, the capillaries and the venules. Pulmonary veno-occlusive disease (PVOD) is classified under group 1 pulmonary arterial hypertension (PAH) as subgroup 1.5 (PAH with features of capillary/venous involvement), and represents a progressive and fatal spectrum of pulmonary vascular disorders. PVOD and pulmonary capillary haemangiomatosis (PCH) can be clinically indistinguishable and often coexist, along with the same risk factors and genetic alterations; they are referred to together as PVOD/PCH in the literature. For brevity, we use the clinical term PVOD in this article. PVOD cannot be distinguished from other forms of PAH based on symptoms and haemodynamics. Risk factors include exposure to toxins/chemotherapeutic drugs and genetic mutation in the EIF2AK4 gene. Radiographic features such as mediastinal adenopathy, centrilobular ground-glass opacities, and interlobular septal thickening, along with the presence of hypoxia and reduced diffusion capacity of the lung may be required for a clinical diagnosis of PVOD, as lung biopsy carries a high risk for bleeding. Characteristic histological findings include narrowing/occlusion of small pulmonary veins. The development of pulmonary oedema with pulmonary vasodilator therapy limits therapeutic options for PVOD. With limited treatment options, lung transplantation remains the only curative treatment.