Telomere-mediated lung disease

Parenchymal lung disease is the fourth leading cause of death in the United States; among the top causes, it continues on the rise. Telomeres and telomerase have historically been linked to cellular processes related to aging and cancer, but surprisingly in the recent decade, genetic discoveries have linked the most apparent manifestations of telomere and telomerase dysfunction in humans to the etiology of lung disease: both idiopathic pulmonary fibrosis and emphysema. The short telomere defect is pervasive in a subset of idiopathic pulmonary fibrosis (IPF) patients, and human IPF is the phenotype most intimately tied to germline defects in telomere maintenance. One-third of families with pulmonary fibrosis carries germline mutations in telomerase or other telomere maintenance genes, and one half of patients with apparently sporadic IPF have short telomere length. Beyond explaining genetic susceptibility, short telomere length uncovers clinically relevant syndromic extrapulmonary disease including a T cell immunodeficiency and a propensity to myeloid malignancies. Recognizing this subset of patients who shares a unifying molecular defect has provided a precision medicine paradigm wherein the telomere-mediated lung disease diagnosis provides more prognostic value than histopathology or multi-disciplinary evaluation. Here, we critically evaluate this progress emphasizing how the genetic findings puts forth a new pathogenesis paradigm of age-related lung disease that links telomere abnormalities to alveolar stem senescence, remodeling and defective gas exchange.