Pulmonary hypertensive vasculopathy in parenchymal lung diseases and/or hypoxia: Number 1 in the Series "Pathology for the clinician" Edited by Peter Dorfmüller and Alberto Cavazza

Abstract

Pulmonary hypertension (PH) with complicating chronic lung diseases and/or hypoxia falls into group 3 of the updated classification of PH. Patients with chronic obstructive lung disease (COPD), diffuse lung disease (such as idiopathic pulmonary fibrosis (IPF)) and with sleep disordered breathing are particularly exposed to the risk of developing PH. Although PH in such a context is usually mild, a minority of patients exhibit severe haemodynamic impairment, defined by a mean pulmonary arterial pressure (mPAP) of ≥35 mmHg or mPAP values ranging between 25 mmHg and 35 mmHg with a low cardiac index (<2 L·min^-1·m^-2). The overlap between lung parenchymal disease and PH heavily affects life expectancy in such a patient population and complicates their therapeutic management. In this review we illustrate the pathological features and the underlying pathophysiological mechanisms of pulmonary circulation in chronic lung diseases, with an emphasis on COPD, IPF and obstructive sleep apnoea syndrome.

FIGURE 1

Small pulmonary arteries exhibiting irregular intimal and medial thickening within emphysematous lung parenchyma. Haematoxylin–eosin–saffron staining. Scale bar=100 µm.

FIGURE 2

a) Actin immunostaining of a remodelled small pulmonary artery. The neointima is thickened by the affluence of cells phenotypically similar to smooth muscle cells (SMC-like cells), expressing actin. b) Desmin immunostaining of the same remodelled pulmonary artery. The neointimal SMC-like cells do not express desmin, unlike medial smooth muscle cells. Both images courtesy of P. Dorfmüller, Hôpital Marie Lannelongue, Le Plessis Robinson, France. Scale bars=100 µm.

FIGURE 3

a) Small pulmonary arteries within a fibrotic area (usual interstitial pneumonia lung). The narrowing of the vascular lumen is the result of both intimal fibrosis and medial smooth muscle increase. Haematoxylin–eosin–saffron staining. Scale bar=250 μm. b) Remodelled small pulmonary arteries outside fibrosis in usual interstitial pneumonia lung. Haematoxylin–eosin–saffron staining. Scale bar=200 μm.