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Pulmonary hypertension and pulmonary vascular remodeling (PVR) are common in many lung diseases leading to right ventricular dysfunction and death. Differences in PVR result in significant prognostic divergences in both the pulmonary arterial and venous compartments, as in pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease (PVOD), respectively. Our goal was to identify compartment-specific molecular hallmarks of PVR, considering the risk of life-threatening pulmonary edema in PVOD, if treated by conventional pulmonary hypertension therapy. Formalin-fixed and paraffin-embedded tissues from fresh explanted human lungs of patients with PVOD (n = 19), PAH (n = 20), idiopathic pulmonary fibrosis (n = 13), and chronic obstructive pulmonary disease (n = 15), were analyzed for inflammation and kinome-related gene regulation. The generated neuronal network differentiated PVOD from PAH samples with a sensitivity of 100% and a specificity of 92% in a randomly chosen validation set, a level far superior to established diagnostic algorithms. Further, various alterations were identified regarding the gene expression of explanted lungs with PVR, compared with controls. Specifically, the dysregulation of microtubule-associated serine/threonine kinase 2 and protein-o-mannose kinase SGK196 in all disease groups suggests a key role in pulmonary vasculopathy for the first time. Our findings promise to help develop novel target-specific interventions and innovative approaches to facilitate clinical diagnostics in an elusive group of diseases., (Copyright © 2020 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Pulmonary capillary haemangiomatosis (PCH) is a rare and incompletely understood histopathological finding characterised by abnormal capillary proliferation within the alveolar interstitium, which has long been noted to share many overlapping features with pulmonary veno-occlusive disease (PVOD). But are PCH and PVOD distinct entities that occur in isolation, or are they closely intertwined manifestations along a spectrum of the same disease? The classic clinical features of both PCH and PVOD include signs and symptoms related to pulmonary hypertension, hypoxaemia, markedly impaired diffusion capacity of the lung and abnormal chest imaging with ground glass opacities, septal lines and lymphadenopathy. In recent years, increasing evidence suggests that the clinical presentation, histopathological features, genetic substrate and pathobiological mechanisms of PCH and PVOD are overlapping and usually indistinguishable. The discovery of biallelic mutations in the eukaryotic translation initiation factor 2 α kinase 4 ( EIF2AK4 ) gene in heritable PCH and PVOD greatly advanced our understanding of the overlapping nature of these conditions. Furthermore, recognition of PCH and PVOD-like changes in other pulmonary vascular diseases and in conditions that cause chronic pulmonary venous hyper-perfusion or hypertension suggests that PCH/PVOD may develop as a reactive process to various insults or injuries to the pulmonary vasculature, rather than being primary angiogenic disorders., Competing Interests: Conflict of interest: J. Weatherald reports grants, personal fees and non-financial support from Janssen Inc. and Actelion, personal fees and non-financial support from Bayer, personal fees from Novartis, and grants from Alberta Lung Association Canadian Vascular Network, European Respiratory Society and Canadian Thoracic Society, outside the submitted work. Conflict of interest: P. Dorfmüller has nothing to disclose. Conflict of interest: F. Perros has nothing to disclose. Conflict of interest: M-R. Ghigna has nothing to disclose. Conflict of interest: B. Girerd has nothing to disclose. Conflict of interest: M. Humbert reports personal fees and non-financial support from Acceleron, grants and personal fees from Bayer and GSK, and personal fees from Actelion, Merck and United Therapeutics, outside the submitted work. Conflict of interest: D. Montani reports grants and personal fees from Actelion and Bayer, and personal fees from GSK Pfizer, MSD and Chiesi, outside the submitted work., (Copyright ©ERS 2020.)

Pulmonary veno-occlusive disease (PVOD) is a rare entity with non-specific signs and symptoms and is nearly always associated with a dismal prognosis. This review will first consider pulmonary hypertension in general and then will focus on PVOD specifically with particular attention to the pathophysiology of the disease. Classically PVOD is described as a disease primarily involving obstructed venules, with the arterial side of the circulation involved to a lesser degree. This article discusses the demographics of affected individuals; the ways in which an accurate diagnosis can be made, including imaging features; predisposing diseases and associated disorders; and potential treatment.

In 1998, during the Second World Symposium on Pulmonary Hypertension (PH) held in Evian, France, a clinical classification of PH was proposed. The aim of the Evian classification was to individualize different categories sharing similarities in pathophysiological mechanisms, clinical presentation, and therapeutic options. The Evian classification is now well accepted and widely used in clinical practice, especially in specialized centers. In addition, this classification has been used by the U.S. Food and Drug Administration and the European Agency for Drug Evaluation for the labeling of newly approved medications in PH. In 2003, during the Third World Symposium on Pulmonary Arterial Hypertension held in Venice, Italy, it was decided to maintain the general architecture and philosophy of the Evian classification. However, some modifications have been proposed, mainly to abandon the term "primary pulmonary hypertension" and to replace it with "idiopathic pulmonary hypertension"; to reclassify pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis; to update risk factors and associated conditions for pulmonary arterial hypertension and to propose guidelines in order to improve the classification of congenital systemic-to-pulmonary shunts.