Definition
• Rare form of pulmonary arterial hypertension with prominent venous involvement
Clinical features
Epidemiology
• Affects males more frequently than females
Presentation
• Shortness of breath
• Increased pulmonary arterial pressure
• Chest CT may demonstrate thickened septal lines, lymph node enlargement, and nodular or ground-glass opacities
Prognosis and treatment
• The prognosis is poor; lung transplantation is the only definitive treatment
• Pulmonary edema may develop with treatment with prostacyclin analogues
Pathology
Histology
• Pulmonary veins are located in the septa, and preseptal venules can be identified by their relationship with these veins
• Small peripheral vessels with a single elastic lamina and without a clearly accompanying airway cannot be definitively identified as venules or arterioles unless serial sections are performed to identify the associated artery or vein
• Occlusion of small pulmonary veins and/or venules with fibrous tissue, which may be sclerotic or edematous, concentric or eccentric, or resemble recanalizing thrombi
• Involvement of veins and venules is patchy; thus, thorough sampling is required
• Obstructed venules may be surrounded by congested, dilated capillaries
• Affected veins may become arterialized, developing an internal elastic lamina
• Calcium or iron deposition on the elastic lamina may be present with or without a giant cell reaction
• Arteries and arterioles may show medial hypertrophy or intimal fibrosis
• Nonspecific signs suggestive of PVOD include septal edema and septal fibrosis, dilated lymphatics, and hemosiderin-laden macrophages
Immunopathology/special stains
• Elastic and trichrome stains highlight venous and arterial changes
Main differential diagnoses
• Pulmonary capillary hemangiomatosis: increased numbers of capillaries without marked venous involvement
• Pulmonary arterial hypertension: no or minimal venous involvement
• Systemic vasculitis involving the lung: mainly affects arteries
Fig 1 Pulmonary venoocclusive disease. Thickened pulmonary veins are present in the interlobular septum extending from the pleural surface (A) with only a slit-like lumen remaining (B).
Fig 2 Pulmonary venoocclusive disease. Edematous fibrous tissue causing venous occlusion (A, trichrome stain; B, H&E; C, elastic stain) demonstrating variable involvement from focal to partial to complete occlusion.
Fig 3 Pulmonary venoocclusive disease. Focal capillary distension secondary to venous occlusion.