Diagnosis and Management of TBD

Author

Based on Franke, Ferrer & Patnaik — Haematologica, March 2026

Published

August 19, 2026

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Telomere Biology Disorders

A comprehensive visual review of diagnosis, manifestations, and emerging therapies

<span class="pill pill-blue">Short Telomere Syndromes</span>
<span class="pill pill-teal">Clonal Hematopoiesis</span>
<span class="pill pill-green">Novel Therapeutics</span>

Overview

Telomere Biology Disorders (TBD) are a heterogeneous group of inherited conditions characterised by impaired telomere maintenance. The clinical spectrum spans bone marrow failure, pulmonary fibrosis, liver disease, and cancer predisposition — making timely diagnosis and multidisciplinary management essential.

Key Definitions

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Telomere Biology Disorders (TBD)

Syndromes characterised by critically short telomeres leading to accelerated ageing, bone marrow failure, pulmonary fibrosis, and malignancy.

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Cancer Predisposition with Long Telomeres (CPLT)

Distinct from TBD — variants causing abnormally elongated telomeres enabling uncontrolled cellular proliferation and elevated cancer risk.

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Clonal Hematopoiesis (CH)

Clonal expansion of HSPCs via somatic mutations conferring a fitness advantage under bone marrow stress from progressive telomere shortening.

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Genetic Anticipation

Successive generations present with shorter baseline telomere lengths, causing earlier onset and increased severity of TBD manifestations.


The Telomere Apparatus

Telomere Physiology Across the Lifespan

Figure 5.1: Telomere length dynamics across the human lifespan. Ultra-short telomeres (<1.6 kb) accumulate with age and drive cellular senescence.

Key Molecular Components

Table 5.1: Core components of the telomere apparatus and TBD gene associations
Complex Component Role TBD Gene
Telomerase TERT Catalytic reverse transcriptase subunit ✓
Telomerase TERC RNA template for telomere synthesis ✓
Telomerase DKC1 (Dyskerin) Stabilises TERC; telomerase assembly ✓
Telomerase NOP10 Telomerase assembly ✓
Telomerase NHP2 Telomerase assembly ✓
Telomerase PARN Controls hTR levels; aids maturation ✓
Shelterin TIN2 (TINF2) Core scaffold; anchors TRF1/TRF2/TPP1 ✓
Shelterin TPP1 (ACD) Docks telomerase to telomere ✓
Shelterin POT1 Binds single-stranded 3′ overhang ✓
Shelterin RAP1 Binds TRF2; chromosome-end protection –
CST CTC1 C-strand fill-in; halts overextension ✓
CST STN1 C-strand fill-in ✓
CST TEN1 C-strand fill-in –
Other RTEL1 Unwinds G-quadruplexes; T-loop resolution ✓
Other RPA1 Stabilises single-stranded telomeric DNA ✓
Other ZCCHC8 hTR maturation ✓

Diagnostic Landscape

Telomere Length Measurement Methods

Figure 6.1: Relative comparison of TL measurement methods across key dimensions (10 = best). ★ = CLIA-certified for clinical use.

Clinical Pearl: Flow-FISH is the only CLIA-validated assay, with 80% sensitivity and 85% specificity for TL <10th percentile. Approximately 20–40% of adult TBD patients will have no identifiable germline pathogenic variant.


Genetic Architecture

TBD Gene Landscape by Molecular Complex

Figure 7.1: TBD-associated genes by affected complex. Bubble size reflects the number of associated clinical disorders.

Cancer Risk

Observed / Expected Malignancy Ratios in TBD

Figure 8.1: Observed/Expected cancer ratios in TBD cohorts (95% CI shown). Note the log scale — MDS and tongue SCC carry dramatically elevated risks.

Cancer Surveillance: TBD patients face an estimated 3-fold higher overall cancer risk vs. the general population. MDS risk may exceed 578× expected rates in dyskeratosis congenita cohorts. Autosomal recessive and X-linked inheritance patterns carry the most pronounced risk.


Clonal Hematopoiesis in TBD

Critically short telomeres impose unique fitness constraints on HSPCs, driving a CH landscape that differs markedly from age-related CH. Somatic mutations can be either adaptive (restoring telomere function) or maladaptive (risking haematologic malignancy).

Figure 9.1: CH mutation types in TBD classified by functional outcome. Adaptive mutations attempt to restore telomere function; maladaptive mutations risk progression to MDS/AML.

Transplantation Outcomes

Figure 10.1: One-year post-transplant survival rates across organ systems in TBD patients.

Screening Guidelines

🩸 Hematologic Monitoring

  • CBC at baseline and annually (more frequent if cytopenias)
  • Annual bone marrow aspirate + biopsy
  • Cytogenetics + NGS molecular genetics
  • Error-corrected sequencing for adaptive/maladaptive CH variants

🫁 Pulmonary

  • Annual pulmonary function testing from diagnosis
  • Low threshold for HRCT chest
  • Pulmonology referral for any PFT decline

🫀 Hepatic

  • Annual liver function tests
  • MR elastography (preferred) or FibroScan
  • Evaluate for NRH and portal hypertension

🔍 Cancer Surveillance

  • Monthly self-exam (skin, breast)
  • Annual dermatologist skin cancer screen
  • Annual ENT: flexible laryngoscopy
  • Periodic gynecological / anogenital screen
  • Standard age-appropriate screening (breast, colon, prostate)

🦴 Bone, Dental & Immunizations

  • Periodic DEXA for bone density
  • Routine dental screening
  • Ensure immunizations are current

📚 Resources

  • Team Telomere — patient advocacy, education & financial support
  • Mayo Clinic TBD Clinic — multidisciplinary care

Future Directions

01

ZSCAN4 Gene Therapy

EXG34217 (Phase I/II, Cincinnati). Ex vivo telomere elongation in CD34⁺ HSPCs demonstrated; peripheral blood TL effect still under evaluation. (Myers et al., NEJM Evidence 2025)

02

TINF2 CRISPR Editing

Frameshift editing into HSPCs renders the faulty TINF2 allele ineffective, restoring TL and increasing proliferative capacity without transformation risk. (Choo et al., Blood 2022)

03

PAPD5/7 Inhibition

RG7834 restores TERC levels and TL in DKC1^A353V variant cells by inhibiting the PAPD5/7 polymerases involved in hTR degradation. (Shukla et al., Blood Adv. 2020)

04

GSK3 Inhibition

CHIR99021 enhances telomerase activity and corrects telomere dysfunction in iPSC-derived type II alveolar epithelial cells — relevant for TBD-associated PF. (Fernandez et al., eLife 2022)

05

Nucleoside Supplementation

Phase I (Boston Children’s, NCT06817590): enteral deoxycytidine + deoxythymidine to elongate telomeres through nucleoside precursor availability.

06

Low-dose Danazol (NIH)

NCT03312400: recruiting TBD patients for 400 mg danazol to optimise dosing and balance telomere elongation against known adverse metabolic and endocrine effects.

Safety: Any therapy causing unregulated telomerase reactivation risks oncogenesis — TERT upregulation is present in ~90% of all human cancers. Gene-based therapies must carefully balance telomere rescue with tumorigenic risk.


Summary Statistics

Figure 13.1: Key numerical landmarks in TBD from this review.