Telomere syndromes, also known as short telomere syndromes are a complex group of diseases whose common factor is that the telomeres, short pieces of DNA that are located at each end of a chromosome, are abnormally short or break down at an accelerated rate. The telomere syndromes have been linked to a number of disease such as cancer, the various bone marrow failure syndromes, birth defects, and even premature aging.
Definition & Facts
Telomeres are caps at the end of DNA strands that protect the chromosomes. Telomeres get progressively shorter the more a cell is reproduced, which results in the aging process.
Telomere syndromes are so rare that there is very little data to indicate how often they occur. Abnormal telomeres were first identified when examining cells taken from children with a very rare condition called dyskeratosis congenita, which causes abnormalities in the cells of the skin, mouth, and nails.
Since that time telomere syndromes have been implicated in many forms of childhood and adult cancers, birth defects, inherited disorders affecting the skin, nails, cancers arising from the cells that line the digestive tract, and even as contributing in part to progeria, a condition characterized by abnormally fast aging in children.
Symptoms & Complaints
Telomere syndromes are implicated in causing a condition called idiopathic pulmonary fibrosis. The symptoms of idiopathic pulmonary fibrosis are related to the buildup of abnormal fibrous tissue in the lungs. They usually include poor exercise tolerance, difficulty breathing, cyanosis (a bluish color of the lips and other mucous membranes caused by a lack of oxygen in the bloodstream) that is apparent even at rest, and failure of the right-sided cardiac muscles. Idiopathic pulmonary fibrosis may progress to the point that heart-lung transplantation becomes necessary. Short telomeres are also seen in many childhood cancers.
Telomere syndromes are the result of genetic mutations. Affected genes include TERT, TR, and DKC1. Depending on the syndrome, genetic mutations may be inherited via autosomal recessive inheritance, autosomal dominant inheritance, X-linked recessive inheritance, or as a result of de novo mutations.
Diagnosis & Tests
The presence of the telomere syndromes is sometimes apparent at birth, but these syndromes are usually diagnosed when symptoms of another condition are being investigated. Although a telomere syndrome may be the underlying cause of a condition, the diagnosis of a telomere syndrome is usually not made until after it appears in the form of a related condition.
A diagnosis of one of the telomere syndromes is based on a combination of medical history, physical examination, and laboratory tests. Definitive diagnosis of a telomere syndrome requires that the presence of short abnormal telomeres be confirmed by observing short or otherwise abnormally-shaped telomeres by use of an electron microscope, but diagnosis may require the use of sophisticated DNA studies that are usually available at most university-affiliated or medical school teaching hospitals.
Treatment & Therapy
Treatment of telomere syndromes varies depending on the syndrome. Androgens may be helpful for those struggling from bone marrow failure. Corticosteroids and hematopoietic growth factors may be used to treat dyskeratosis congenita. Bone marrow transplant and liver transplants may also be recommended depending on the type of disorder and severity of the condition.
Prevention & Prophylaxis
A diagnostic amniocentesis should be offered to women with a telomere syndrome or if the father has inherited one of the syndromes. As noted earlier, treatment of the telomere syndromes is directed at the disease the syndrome causes.