A proportion of patients with interstitial lung diseases (ILDs) are at risk of developing a progressive-fibrosing phenotype, which is associated with a deterioration in lung function and early mortality. In addition to idiopathic pulmonary fibrosis (IPF), fibrosing ILDs that may present a progressive phenotype include idiopathic nonspecific interstitial pneumonia, connective tissue disease-associated ILDs, hypersensitivity pneumonitis, unclassifiable idiopathic interstitial pneumonia, ILDs related to other occupational exposures and sarcoidosis. Corticosteroids and/or immunosuppressive therapies are sometimes prescribed to patients with these diseases. However, this treatment regimen may not be effective, adequate on its own or well tolerated, suggesting that there is a pressing need for efficacious and better tolerated therapies. Currently, the only approved treatments to slow disease progression in patients with IPF are nintedanib and pirfenidone. Similarities in pathobiological mechanisms leading to fibrosis between IPF and other ILDs that may present a progressive-fibrosing phenotype provide a rationale to suggest that nintedanib and pirfenidone may be therapeutic options for patients with the latter diseases.This review provides an overview of the therapeutic options currently available for patients with fibrosing ILDs, including fibrosing ILDs that may present a progressive phenotype, and explores the status of the randomised controlled trials that are underway to determine the efficacy and safety of nintedanib and pirfenidone.

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The 2013 American Thoracic Society/European Respiratory Society consensus classification update of the idiopathic interstitial pneumonias (IIP) included several important modifications to the organization and spectrum of the diseases that were proposed in an earlier multidisciplinary consensus document in 2002. The histopathology of the now 'major' and 'rare' IIP is presented here with exposition of the newly included entity of a distinctive upper lobe fibrotic lung disease referred to as idiopathic pleuroparenchymal fibro-elastosis. The 'rare histological patterns' of acute fibrinous and organizing pneumonia and bronchio-locentric patterns of interstitial pneumonia are illustrated and discussed. Summary: Pleuroparenchymal fibroelastosis is a newly recognized ands accepted rare form of interstitial lung disease with distinct radiological and pathological appearance. Many cases are idiopathic, but a number are associated with underlying conditions. Familiarity with this entity will prevent confusion with other more recognized forms of fibrosing interstitial pneumonia. Main teaching points: • Pleural thickening and pulmonary parenchy-mal fibrosis begin in the upper zones and progress inferiorly with time • Pathology is distinctive with consolidative fibroelastosis showing demarcation from the uninvolved lung • PPFE may be idiopathic or associated with other pulmonary diseases bs_bs_banner

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Background Angiotensin-converting enzyme 2 (ACE2) is the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which causes COVID-19. Viral entry requires ACE2 and transmembrane protease serine 2 (TMPRSS2). Transcriptomic studies showed that children display lower ACE2 than adults, though gene expression levels do not always correlate with protein levels. We investigated the effect of age on ACE2 and TMPRSS2 protein expression in alveolar type II (AT2) cells in the lungs of children compared to adults. We also analysed the ratio of Ang-(1–7) to Ang II as a surrogate marker of ACE2 activity in the subjects’ lung parenchyma. Methods Ang II and Ang-(1–7) levels and ACE2 and TMPRSS2 protein expression were measured by radioimmunoassay and immunohistochemistry, respectively. Results The amount of ACE2-expressing AT2 cells and ACE2 protein content were lower in children than in adults. Ang II levels were higher in children compared to adults and inversely correlated with the amount of ACE2-expressing AT2 cells. Children presented lower Ang-(1–7)/Ang II ratio than adult suggesting lower ACE2 activity in children. TMPRSS2 protein expression was not influenced by age. Conclusions These results expand on previous transcriptomic studies and may partially explain the low susceptibility of children to SARS-CoV-2 infection. Category of study Clinical original research Impact Children display lower ACE2 protein content and activity compared to adults. Ang II levels were higher in children compared to adults and inversely correlated with the amount of ACE2-expressing AT2 cells TMPRSS2 protein expression was not influenced by age. These results expand on previous transcriptomic studies and may partially explain the low susceptibility of children to SARS-CoV-2 infection.

Aims Angiotensin-converting enzyme (ACE) 2 is the receptor for severe acute respiratory syndrome coronavirus 2 which causes coronavirus disease 2019 (COVID-19). Viral cellular entry requires ACE2 and transmembrane protease serine 2 (TMPRSS2). ACE inhibitors (ACEIs) or angiotensin (Ang) receptor blockers (ARBs) influence ACE2 in animals, though evidence in human lungs is lacking. We investigated ACE2 and TMPRSS2 in type II pneumocytes, the key cells that maintain lung homeostasis, in lung parenchymal of ACEI/ARB-treated subjects compared to untreated control subjects. Main methods Ang II and Ang-(1–7) levels and ACE2 and TMPRSS2 protein expression were measured by radioimmunoassay and immunohistochemistry, respectively. Key findings We found that the ratio Ang-(1–7)/Ang II, a surrogate marker of ACE2 activity, as well as the amount of ACE2-expressing type II pneumocytes were not different between ACEI/ARB-treated and untreated subjects. ACE2 protein content correlated positively with smoking habit and age. The percentage of TMPRSS2-expressing type II pneumocytes was higher in males than females and in subjects under 60 years of age but it was not different between ACEI/ARB-treated and untreated subjects. However, there was a positive association of TMPRSS2 protein content with age and smoking in ACEI/ARB-treated subjects, with high TMPRSS2 protein levels most evident in ACEI/ARB-treated older adults and smokers. Significance ACEI/ARB treatment influences human lung TMPRSS2 but not ACE2 protein content and this effect is dependent on age and smoking habit. This finding may help explain the increased susceptibility to COVID-19 seen in smokers and older patients with treated cardiovascular-related pathologies.

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