In search of markers of treatment failure and poor prognosis in IPAH - the value of mosaic lung attenuation pattern on thin-section CT scans

Despite the development of specific therapies for pulmonary arterial hypertension (PAH) some patients fail to respond to such treatment. One of the potential reasons for the unresponsiveness to targeted therapies may be the presence of fibrous occlusion of small pulmonary veins that accompanies pre-capillary arteriopathy. This type of pathologic change is called pulmonary veno-occlusive disease (PVOD). Underdiagnosed PVOD occurs probably in 5-10% of idiopathic pulmonary hypertension (IPAH) and in a substantial proportion of PAH related to connective tissue diseases (mainly in scleroderma). A definite diagnosis of PVOD requires histological examination of lung sample, but surgical lung biopsy in pulmonary hypertension is combined with high risk of bleeding. Thus major interest is focused on a non-invasive diagnostic approach enabling early recognition of PVOD and referral for lung transplantation. The present review is focused on the radiological features suggestive of PVOD-like vasculopathy in PAH.