Short Telomeres Fail to Separate Inherited from Acquired Aplastic Anemia

A large prospective study from India has found that a quick, inexpensive telomere test widely used in blood disorder clinics cannot reliably tell inherited aplastic anemia apart from the acquired form of the disease. The only exception is a reassuring one: when telomere length looks completely normal, the likelihood of an underlying telomere biology disorder drops dramatically.

Aplastic anemia is a serious condition in which the bone marrow fails to produce enough blood cells. Some cases arise from inherited bone marrow failure syndromes caused by germline mutations, including telomere biology disorders, in which mutations in telomere maintenance genes drive accelerated telomere attrition and multi-organ dysfunction ranging from pulmonary fibrosis and liver cirrhosis to bone marrow failure. Others are acquired, often immune-mediated. The distinction matters clinically: identifying a telomere biology disorder or Fanconi anemia before hematopoietic stem cell transplantation requires modified conditioning regimens to avoid excessive toxicity, and telomere length is also an independent prognostic factor predicting poor response to immunosuppressive therapy, higher relapse rates, clonal evolution, and inferior post-transplant outcomes.

The gold standard for measuring telomeres, flow-FISH, combines flow cytometry with fluorescence in situ hybridization but is often unavailable, technically complex, and costly in resource-constrained settings. Quantitative PCR offers a scalable, cost-effective alternative, yet its diagnostic performance across different germline categories had remained poorly defined in unselected prospective cohorts.

The sequencing placed patients into four categories: 40 patients, or 13.1 percent, with confirmed inherited bone marrow failure syndrome; 19, or 6.2 percent, with a single pathogenic variant in a recessive gene lacking a confirmed second hit; 39, or 12.8 percent, carrying a variant of uncertain significance; and 207, or 67.9 percent, with no qualifying germline variant, treated as acquired aplastic anemia. Overall, 115 patients, or 37.7 percent, had shortened telomeres, with 45, or 14.8 percent, falling into the very shortened range. Notably, telomere shortening was not significantly associated with sex, disease severity, PNH clone positivity, germline category, or peripheral blood counts; age was the only clinical parameter that differed across telomere length categories.

The degree of shortening varied sharply by etiology. Among confirmed carriers of pathogenic variants in telomere biology disorder genes, 71.4 percent, five of seven, had shortened telomeres. By contrast, only 31.6 percent of patients with biallelic variants in Fanconi anemia pathway genes and 37.7 percent of those with acquired disease had shortened telomeres, rates essentially indistinguishable from each other. Among carriers of variants of uncertain significance in telomere biology disorder genes, four of five, or 80 percent, had shortened telomeres, closely mirroring the confirmed carriers, though the authors caution this rests on a very small sample. Across the full inherited disease spectrum, however, telomere length showed no meaningful discriminatory power: the area under the receiver operating characteristic curve was 0.512 against acquired disease, and chi-square testing across all four germline categories found no significant difference in telomere length distribution.

The clinically useful result emerged at the normal end of the distribution. A telomere length above the tenth percentile excluded telomere biology disorder-associated inherited bone marrow failure with a negative predictive value of 98.5 percent against acquired disease and 98.7 percent when genetically indeterminate patients were included in the comparison group. The picture at the abnormal end was far less encouraging. Very shortened telomeres, at or below the first percentile, carried a positive predictive value of only 12.9 percent for telomere biology disorder-associated disease, with sensitivity of 57.1 percent and specificity of 87.0 percent. Critically, 13.0 percent of patients with entirely acquired aplastic anemia and no qualifying germline variant also had very short telomeres, meaning more than one in eight patients with acquired disease shared the telomere phenotype classically associated with constitutional telomere disorders.

The authors attribute this overlap to mechanistic heterogeneity. Telomere shortening in non-telomere inherited syndromes and acquired aplastic anemia reflects secondary hematopoietic stress rather than primary telomerase insufficiency. Prior work has documented postnatal attrition proceeding at 267 base pairs per year in severe aplastic Fanconi anemia, and diverse upstream mechanisms, from stem cell hyperproliferation in Shwachman-Diamond syndrome to DNA repair pathway disruption, all produce telomere shortening indistinguishable from constitutional telomere disease by measurement alone. In acquired aplastic anemia, immune-mediated replicative stress appears to drive progressive shortening, with granulocyte telomere length falling below critical thresholds in untreated disease and normalizing after immunosuppressive therapy, and attrition localized to antigen-expanded CD8-positive T cells.

These background rates carry direct consequences for variant interpretation. A recurring question in genetics is whether a very short telomere measurement can serve as supportive functional evidence when adjudicating a variant of uncertain significance in a telomere biology disorder gene. The study’s data argue for caution: since the same telomere phenotype occurs in more than one in eight patients with entirely acquired disease, very short telomeres cannot be reliably distinguished from constitutionally short telomeres at the individual patient level. The literature reinforces this bidirectional unreliability. In one study, only one of seven aplastic anemia patients with telomeres below the first percentile carried a TERT mutation; in a French nationwide cohort, 13.6 percent of genetically confirmed adult telomere biology disorder index cases had telomeres above the tenth percentile yet showed classic multi-organ disease; and across 194 confirmed index cases, telomere length correlated poorly with both disease expression and penetrance. Some disorders, such as biallelic CTC1 mutations, can cause bone marrow failure without measurable telomere shortening at all.

The authors are equally candid about the statistics of their reassuring finding. Negative predictive value depends mathematically on disease prevalence, and because confirmed telomere biology disorder gene variants were uncommon in this unselected cohort, a high negative predictive value was statistically expected. They therefore report the positive predictive value alongside it throughout to avoid an inflated impression of the test’s standalone power. Nonetheless, because the clinical consequences of a false negative are significant, a rule-out test with very high negative predictive value retains value even at low prevalence, provided it is used explicitly to deprioritize rather than replace definitive germline sequencing. The study had limitations: qPCR has a higher interassay coefficient of variation than flow-FISH, no validated flow-FISH platform was available for direct comparison, the single-center design limits generalizability, and therapeutic response was not assessed.

The practical takeaway is a nuanced one. In unselected patients with aplastic anemia, qPCR-based telomere analysis does not distinguish inherited from acquired disease across the full spectrum of inherited bone marrow failure syndromes, and 65 percent of patients with inherited disease in this cohort had normal telomeres at diagnosis. But a normal result substantially lowers the likelihood of a telomere biology disorder, supporting a potential role as a rule-out-oriented adjunct, particularly in resource-limited settings where flow-FISH and comprehensive genetic testing are not readily accessible. Conversely, a very short telomere may raise the possibility of a telomere biology disorder and justify further directed evaluation, but it alone is insufficient to establish a constitutional telomere disorder, and patients with a suggestive phenotype or family history should undergo appropriate germline evaluation irrespective of telomere results. The authors emphasize that prospective studies assessing the impact of telomere analysis on clinical decision-making, diagnostic efficiency, turnaround time, and cost-effectiveness are needed before it can be recommended as a diagnostic triage strategy, and that direct comparative studies are required to establish how qPCR performs relative to flow-FISH.

Subject of Research: Telomere length measured by qPCR as a diagnostic adjunct for germline mutation status in aplastic anemia

Article Title: Telomere length analysis using qPCR in aplastic anemia: prevalence and predictive value for germline mutation status

Article References: Raina, S., Jain, A., Thakur, V., Balakrishnan, A., Jamwal, M., Bhatia, P., Bansal, D., Malhotra, P., Das, R., & Sreedharanunni, S. (2026). Telomere length analysis using qPCR in aplastic anemia: prevalence and predictive value for germline mutation status. Blood Research, 61(1), Article 58. https://doi.org/10.1007/s44313-026-00182-x

Image Credits: AI Generated

DOI: 10.1007/s44313-026-00182-x

Keywords: aplastic anemia, telomere length, qPCR, germline mutations, telomere biology disorders, inherited bone marrow failure syndrome, variants of uncertain significance, flow-FISH, negative predictive value, bone marrow failure, genetic testing, Telomere