TABLE 2

Comparison of key distinguishing features between pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease (PVOD)

	PAH	PVOD
Genetics
Main gene mutation	BMPR2, ACVRL1, ENG, KCNK3, CAV-1, SMAD9	EIF2AK4
Genetic transmission	Autosomal dominant	Autosomal recessive
Epidemiology
Estimated prevalence	15 cases per million	1–2 cases per million
Sex ratio	Female predominance (∼2:1)	No sex predominance
Smoking	Possible association	More prevalent than idiopathic PAH
Occupational exposure	Absent	Organic solvent (trichloroethylene)
Risk factors
Drugs and toxins	Anorexigens (aminorex, fenfluramine derivatives, benfluorex), dasatanib, interferon	Chemotherapy (alkylating agents)
Associated conditions	Connective tissue disease, congenital heart disease, HIV infection, portal hypertension	Connective tissue disease particularly in systemic sclerosis
Clinical examination
Haemoptysis	Possible	Possible
Auscultatory crackles	Absent	Rare, except in presence of pulmonary oedema
Pleural effusions	Possible	Possible
Right heart catheterisation
mPAP, PAWP, PVR	Increased mPAP, normal PAWP, increased PVR	Increased mPAP, normal PAWP, increased PVR
Acute vasoreactivity testing	∼10% in idiopathic PAH (predicts long-term CCB response)	∼10% (not a predictor of CCB response)
Pulmonary function
FEV₁, FVC, TLC	Normal (possible mild reduction)	Normal (possible mild reduction)
D_LCO, D_LCO/V_A	Normal or mildly reduced	Severe reduction
Resting P_aO₂	Normal or mildly reduced	Often severe reduction
Desaturation on exercise	Often present	Often severe reduction
Imaging
Chest HRCT	Usually normal parenchyma	Centrilobular ground-glass opacities, septal lines, mediastinal lymph node enlargement
V′/Q′ lung scan	Usually normal	Usually normal
Bronchoscopy
BAL	Normal	Possible occult alveolar haemorrhage
Treatment
Targeted PAH therapy	RCTs demonstrating improved haemodynamics, functional capacity and clinical outcomes	Risk of pulmonary oedema Conflicting data from small case series

mPAP: mean pulmonary artery pressure; PAWP: pulmonary artery wedge pressure; PVR: pulmonary vascular resistance; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; TLC: total lung capacity; D_LCO: diffusing capacity of the lung for carbon monoxide; D_LCO/V_A: D_LCO adjusted for alveolar volume; P_aO₂: arterial oxygen tension; HRCT: high-resolution computed tomography; V′/Q′: ventilation/perfusion; BAL: bronchoalveolar lavage; BMPR2: bone morphogenetic protein receptor type 2; ACVRL1: activin A receptor type II-like kinase 1; ENG: endoglin; KCNK3: potassium channel subfamily K member 3; CAV-1: caveolin 1; EIF2AK4: eukaryotic translation initiation factor 2 alpha kinase 4; CCB: calcium channel blocker; RCT: randomised controlled trial.