Natural history of pulmonary fibrosis in two subjects with the same telomerase mutation

Abstract

Previous studies have identified subclinical lung disease in family members of probands with familial pulmonary fibrosis, but the natural history of preclinical pulmonary fibrosis is uncertain. The purpose of this study was to determine whether individuals with preclinical lung disease will develop pulmonary fibrosis. After a 27-year interval, two subjects with manifestations of preclinical familial pulmonary fibrosis, including asymptomatic alveolar inflammation and alveolar macrophage activation, were reevaluated for lung disease. CT scans of the chest, pulmonary function tests, and BAL were performed, and genomic DNA was analyzed for mutations in candidate genes associated with familial pulmonary fibrosis. One subject developed symptomatic familial pulmonary fibrosis and was treated with oxygen; her sister remained asymptomatic but had findings of pulmonary fibrosis on high-resolution CT scan of the chest. High concentrations of lymphocytes were found in BAL fluid from both subjects. Genetic sequencing and analyses identified a novel heterozygous mutation in telomerase reverse transcriptase (TERT, R1084P), resulting in telomerase dysfunction and short telomeres in both subjects. In familial pulmonary fibrosis, asymptomatic preclinical alveolar inflammation associated with mutation in TERT and telomerase insufficiency can progress to fibrotic lung disease over 2 to 3 decades.

Trial registry: ClinicalTrials.gov; No.: NCT00071045; URL: www.clinicaltrials.gov.

Figure 1.

Features of siblings with familial pulmonary fibrosis and a mutation in telomerase reverse transcriptase (TERT). A, Pedigree of the affected family in 1982 (adapted from Reference ) and in 2009. *Indicates subject 1, **Indicates subject 2. B, Representative images from a CT scan of the chest from subject 1, which shows extensive interstitial infiltrates consistent with IPF, and high-resolution CT scan of the chest from subject 2, which shows mild subpleural reticulations and honeycombing consistent with early pulmonary fibrosis. IPF = idiopathic pulmonary fibrosis.

Figure 2.

Bone marrow hypocellularity and bronchoalveolar lymphocytosis. A, Bone marrow biopsy section from subject 1 showing increased fat cells (*) and a hypocellular marrow (20%-30% cellularity) without major dysplastic changes. (Hematoxylin and eosin, original magnification ×10). B, Representative field of a Cytospin preparation of BAL cells stained with Diffquik shows alveolar macrophages (arrows) and lymphocytes (arrowheads) from subject 2. Lymphocytes are markedly increased in the BAL specimen. (Diffquick stain, original magnification ×20, bar 50 μm).

Figure 3.

Telomere mutation and length. A, Heterozygous change in cDNA position 3251 of TERT from guanine to cytosine, resulting in a substitution of arginine to proline at amino acid 1084 of telomerase in subjects 1 and 2. B, Blood leukocyte telomere length (relative T/S ratio) as a function of age of subject 1 and 2 and healthy control subjects. The two probands have an age-adjusted telomere length of less than the first percentile. The curve marks the 50th percentile of telomere length for healthy control subjects as a function of age. T/S ratio = telomere to single-copy gene ratio. See Figure 1 legend for expansion of the other abbreviation.

Figure 4.

Telomerase activity. Telomerase activity was quantified using mutated and WT vectors that were transfected into telomerase-deficient cells. Telomerase activity is significantly reduced in cells with an R1084P mutation in TERT compared with cells expressing WT telomerase and is significantly higher than that in cells that do not express telomerase (n = 6; ***P < .001). Flag = vector without TERT; WT = wild-type. See Figure 1 legend for expansion of the other abbreviation.