Introduction: Pulmonary fibrosis (PF) comprises a heterogeneous group of disorders traditionally classified as idiopathic pulmonary fibrosis (IPF) and non-IPF. Telomere biology disorders (TBDs) are increasingly recognized in PF. Short telomere length (≤10th percentile) in lymphocytes is associated with pathogenic telomere-maintenance gene variants; however, clinical features alone are poor predictors. Since 2019, our institution has implemented routine, clinically indicated telomere length and genetic testing independent of clinical suspicion in patients evaluated for PF.

Objectives: To evaluate the prevalence and clinical implementation of telomere length testing in patients with pulmonary fibrosis over a six-year period at a tertiary center, and to estimate the burden of undiagnosed telomere shortening in this population.

Materials and Methods: We performed a retrospective analysis of consecutive PF patients evaluated between January 1, 2019, and December 31, 2025, who underwent telomere length testing. Patients with SARD-associated interstitial lung disease were excluded. Telomere length was measured in peripheral blood using CLIA-certified Flow-FISH and reported as age-adjusted percentiles. Clinical data were extracted from the electronic medical record.

Results: Among 67,865 PF patients, 739 underwent telomere length testing, increasing from 9 cases in 2019 to 216 in 2025. Of those tested, 366/739 (45.5%) had telomere length <10th percentile in lymphocytes and/or granulocytes, and 88 (24%) had telomere length <1st percentile. The cumulative number of cases with telomere length <10th percentile increased from 5 in 2019 to 413 in 2025.

Sensitivity analyses using conservative prevalence assumptions (5–15%) estimate that 3,393–10,179 PF patients may have telomere length <10th percentile. Lymphocyte-specific analyses, using more conservative assumptions (5–10%), estimate 3,393–6,786 affected patients.

Conclusions: Short telomere length is common and under-recognized in PF. Despite increased testing, many affected patients remain unidentified. Routine telomere length assessment should be incorporated into standard PF evaluation, recognizing potential non-genetic influences such as smoking, inflammation, and environmental exposures.