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The following is a summary of “Alveolar stem cell exhaustion, fibrosis, and bronchiolar proliferation” related entities. A narrative review,” published in the September 2024 issue of Pulmonology by Chilosi et al.

In recent decades, idiopathic interstitial pneumonia (IIPs) classification has primarily relied on clinical, radiological, and histopathologic features to differentiate between various entities, predict clinical behavior, and guide treatment. However, this phenotype-based approach falls short in distinguishing idiopathic conditions from similar disorders with known causes and does not adequately inform the development of targeted treatments. Advances in molecular morphology, single-cell RNA sequencing, and genetic and molecular profiling have illuminated the underlying pathobiological pathways of these disorders, facilitating the identification of distinct endotypes and enabling the application of precision medicine concepts akin to those in oncology. 

This shift towards a mechanistic-based classification system has led to the emergence of more effective therapeutic strategies and improved prognoses. Given the limitations of the current ATS/ERS classification system, which marks a significant milestone in interstitial lung disease (ILD) management, researchers propose a new classification framework based on pathogenetic processes. The analysis identifies four main pathogenetic categories: entities characterized by senescence, sharing clinical features with idiopathic pulmonary fibrosis (IPF), including subsets of fibrosing hypersensitivity pneumonitis (HP) and collagen vascular disease-associated ILDs; disorders with a potential for fibrotic evolution driven by a clonal background; conditions where inflammation is a central factor, potentially responsive to anti-inflammatory and immunomodulatory therapies; and monogenic entities where senescence or alveolar stem cell exhaustion is not the primary pathogenetic mechanism. 

This narrative review, the first in a series of four, synthesizes current knowledge from PubMed searches using terms such as ‘idiopathic pulmonary fibrosis/classification,’ ‘pathogenesis,’ and ‘RNA sequencing,’ among others, to support the development of this new classification scheme.

Source: sciencedirect.com/science/article/pii/S2531043724000928