• Joanne J van der Vis, Jasper J van der Smagt, Frederic A M Hennekam, Jan C Grutters, and van MoorselColine H MCHMDepartment of Pulmonology, ILD Center of Excellence, St Antonius Hospital, Nieuwegein; Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands..
• Department of Pulmonology, ILD Center of Excellence, St Antonius Hospital, Nieuwegein; Department of Clinical Chemistry, ILD Center of Excellence, St Antonius Hospital, Nieuwegein. Electronic address: a.vandervis@antoniusziekenhuis.nl.
• Chest. 2020 Aug 1; 158 (2): 612-619.

BackgroundGermline mutations in the gene encoding TERT cause haploinsufficiency with subsequent telomere shortening. TERT mutations are associated with short telomere syndromes, such as pulmonary fibrosis (PF), which is often the first manifestation of a short telomere syndrome. Telomere length is heritable, and progeny of telomerase mutation carriers are known to have shorter telomeres. In families with TERT mutations, genetic anticipation, the earlier onset of symptoms with successive generation, is described. Little is known on the number of generations that may pass before disease occurs in families with a TERT mutation.Research QuestionThe objective of this study was to determine classification and origin of the new TERT c.2005T mutation from population genetics and genealogic data and disease history of affected families.Study Design And MethodsThe TERT gene of 240 patients with familial PF was screened for mutations. Additionally, 1,015 patients with PF, 1,237 patients with an interstitial lung disease (ILD) without PF, and 529 healthy control subjects were genotyped for the TERT c.2005C>T mutation. Genealogic research was performed on all patients who carried the TERT c.2005T mutation.ResultsWe detected the TERT c.2005T (p.Arg669Trp) mutation in 13 out of 1,255 patients with PF vs none of the patients with ILD without PF and the healthy control subjects. Genealogic research connected four of the TERT c.2005T mutation carriers to a common ancestor who lived seven generations back, spanning a period of 300 years.InterpretationThe TERT c.2005T mutation is a pathogenic mutation and associates with PF. This study learns that a latency period of > 300 years may pass before the cumulative effect of telomere shortening eventually leads to PF. This finding underlines the complexity of the clinical interpretation of TERT mutations because, not the presence of the mutation, but the result of genetic anticipation, is associated with disease. Therefore, multidisciplinary discussion between pulmonary physicians, clinical geneticists, and genetic laboratory experts is recommended.Copyright © 2020 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

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