For Physicians — Telomeres and Telomerase Deficiency
Telomere disorders are caused by extremely short telomeres. When telomeres become extremely short, cells can no longer divide effectively. An inherited mutation in the gene that produces the telomere lengthening enzyme called telomerase disables the enzyme and causes telomeres to shorten at a faster rate.
RepeatDx’s Flow-FISH procedure has been shown to be a valuable screening test for inherited telomere maintenance deficiencies. This interest is driven by several recent peer-reviewed scientific publications showing that telomere length analysis measured by Flow-FISH can be used to identify individuals with various forms of inherited telomerase deficiency and to distinguish carriers of mutations in telomerase genes and in genes encoding telomere binding proteins from individuals without such abnormalities. More information on RepeatDx and our Flow-Fish technology can be found in the FAQ section.
The clinical sensitivity and specificity for Flow-FISH telomere length analysis have been defined for the diagnosis of dyskeratosis congenita. Telomere biology disorders, an inherited genetic condition, is associated with Low (L) or Very Low (VL) leucocyte telomere length in several leucocyte subsets in the presence of specific symptoms and/or significant family history. No critical values have been defined outside this specific clinical application (telomere biology disorders) to date. However, research reports published in the scientific and medical literature point to other potentially clinically valuable applications (for which critical values have not been formally established).
A guideline for the diagnosis and management of Dyskeratosis Congenita and Telomere Biology Disorders and edited by Drs. Sharon A. Savage and Elizabeth F.Cook can be found on the DC Outreach website.
Bone Marrow Donors Screening
Findings have indicated that telomere length shortens rapidly in patients immediately following hematopoietic stem cells transplantation. These findings suggest that it is important to identify donors with healthy telomere maintenance that are within the biologically tolerable range of the recipient. However, if hematopoietic stem cells from older telomere maintenance deficient donors are transplanted into younger patients, the telomeres may become too short resulting in cellular senescence and bone marrow failure.
Pulmonary fibrosis (PF) has been linked molecularly by abnormal telomere maintenance. Studies have found that Very Low leukocyte telomere length is independently associated with worse survival for PF patients. Reasons for testing include:
- Diagnostic tool for patients and family with familial and idiopathic pulmonary fibrosis
- Telomere length is associated with transplant free survival
- Aid in disease course prediction
- Risk assessment for lung transplantation
- Cost of telomere test is less than genetic testing and pulmonary function tests
RepeatDx provides telomere testing for individual who, under physician supervision, may be interested in adding telomere length measurements as a biomarker for monitoring other diseases or family history risks. Due to regulator requirements, RepeatDx cannot provide diagnostic testing direct to consumers. Before acquiring a blood sample, the requisition form must to be reviewed and signed by a practicing licensed physician. RepeatDx does not recommend or approve treatments designed to optimize telomere modifications.
For Patients — Telomeres and Inherited Deficiencies
All chromosomes have protective structures located at their tips called telomeres. These tips normally shorten, as a person gets older. In some individuals the length is abnormally short or the shortening process is accelerated (in some cases both issues can occur). A telomere length analysis test is a blood test that measures the length of the telomeres, and the information collected is used to confirm a diagnosis when a person has signs or symptoms that may be due to a telomere deficiency.
The Flow-FISH telomere length measurements used by RepeatDx have been shown to be valuable as a screening test for inherited telomere biology disorders resulting from mutations in specific genes.
Inherited deficiencies where telomere analysis is used in clinical diagnosis include bone marrow failure, dyskeratosis congenita, aplastic anemia, acute myeloid leukaemia, immune deficiencies, and pulmonary fibrosis. These defects may be caused by unknown stressors or inherited deficiencies in genes involved in telomere maintenance or telomere biology. Other medical conditions where telomere length investigations and ongoing research may benefit clinical care include chronic lymphocytic leukaemia and cardiovascular diseases.
For patients and families wanting more information on telomere biology disorders, visit the Dyskeratosis Congenita Outreach website.