Acute ischaemic lung injury due to pulmonary vascular obstruction

We have encountered cases of a distinctive myxomatous alveolar wall thickening around pulmonary infarctions, and have termed it 'acute ischaemic lung injury' (AILI). In this study we determined if pulmonary infarction is the only cause of AILI and have elucidated its histological features.

We examined 2941 cases that underwent lobectomy, surgical lung biopsies for nodular lesions or autopsies between 1994 and 2014. Cases were divided into pulmonary infarction and non-infarction groups. The histological features of AILI sought were lobule-based alveolar wall thickening (myxomatous or fibrous) with epithelial metaplasia and negligible inflammation. In order to characterize AILI further, we performed immunohistochemical staining using several antibodies. Thirty-four of 69 cases in the infarction group (mean age 57.1 years, 30 males) had AILI, whereas only one (but with vascular obstruction) of the remaining 2872 in the non-infraction group had AILI. AILI was located around infarctions. Separation of the epithelial and endothelial basement membranes of the alveolar wall was observed in 75% of cases.

AILI is associated almost exclusively with lung infarction, caused presumably by vascular obstruction. We consider AILI to represent a distinct lung lesion other than pulmonary haemorrhage and infarction.