Connective tissue disease-related pulmonary arterial hypertension - a pathology beyond the precapillary vessels

Pulmonary arterial hypertension (PAH) is a fatal and not uncommon complication in the setting of connective tissue diseases (CTD). Clinical and radiological signs of PVOD are commonly present in systemic slerosis (SSc) and involvement of the post-capillary vasculature is increasingly discussed in other forms of CTD such as Mixed Connective Tissue Disease and Lupus Erythematodes. The histological pattern of pulmonary veno-occlusive disease is frequently observed in CTD-related PAH. PVOD is histologically characterized by an obstruction of small pulmonary veins, which contribute to increasing pulmonary vascular resistance, ultimately leading to right heart failure and death. In clinical practice, it is difficult to distinguish pulmonary hypertension from PVOD. However, significant progress in the diagnosis of this rare condition has been made in recent years. Today, it is possible to approximate the diagnosis of idiopathic PVOD with non-invasive tools. This approach has recently been described in patients suffering from CTD-related PAH and suspicion of underlying PVOD. The present review provides an update on clinical, radiological and pathological characteristics of pulmonary veno-occlusive disease in the context of CTD.