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Dyskeratosis Congenita

Males affected more than females

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Updated July 08, 2008

Dyskeratosis congenita is an inherited genetic skin condition characterized by network-like dark patches, abnormal nail growth, lesions in the mouth, and progressive bone marrow failure.

Dyskeratosis congenita is caused by a mutated gene, DKC1, located on the X (female) chromosome, and in most cases is inherited as an X-linked recessive disorder. Males have one X and one Y chromosome and females have two X chromosomes. If a male inherits the DKC1 genetic defect on his single X chromosome, he will have dyskeratosis congenita. However, a female would need to inherit two defective X chromosomes in order to have the disorder. Because of this inheritance pattern, the ratio of men to women affected by the disorder is approximately 10:1.

About 180 individuals with dyskeratosis congenita have been reported in the worldwide medical literature. They have come from many different countries and ethnic backgrounds.

Symptoms

The typical symptoms of dyskeratosis congenita involve the skin, nails, and mucous membranes, as well as bone marrow failure.
  • Skin - patches of darker skin in a spotted (mottled) or network (reticulated) pattern, usually on the upper trunk, neck, and face
  • Nails - ridges and fissures in the nails, with weakening, thinning, and distortion of the fingernails, then the toenails
  • Mucous membranes - white patches (leukoplakia) on the insides of the cheeks, tongue, and upper throat; these patches may become cancerous later on
  • Bone marrow failure - inability of the bone marrow to produce enough white blood cells (needed for immunity), red blood cells (needed to carry oxygen and iron), and platelets (needed for clotting)
Individuals with dyskeratosis congenita may have other symptoms such as hair loss, tooth cavities, and problems with their lungs. Having a weakened immune system may lead to serious infections or the development of cancer. Learning difficulties, mild-to-moderate mental retardation, or short stature may be present.

Diagnosis

In the known individuals with dyskeratosis congenita, the skin and mucous membrane symptoms typically developed between ages 5 and 15. Symptoms of bone marrow failure began in childhood as well. The typical symptoms will point to the diagnosis of dyskeratosis congenita, as well as having a family history of the disorder. Genetic testing can identify the DKC1 gene mutation.

The individual with dyskeratosis congenita should be tested for bone marrow failure and other serious complications such as cancerous lesions in the mouth and lung disease.

Treatment

The most serious aspect of dyskeratosis congenita, bone marrow failure, is treated with Epogen (epoetin alfa), a medication that stimulates the production of red blood cells, and Neupogen (filgrastim), a medication that stimulates the production of white blood cells. The only long-term cure is bone marrow transplant from a healthy person, often a family member. However, if an individual with dyskeratosis congenita has lung disease, he or she may not be a good candidate for a bone marrow transplant.

Genetic testing

Since the DKC1 gene mutation has been associated with dyskeratosis congenita, individuals in the family of a person affected by the disorder can have genetic testing, and females who are carriers of the defective gene can be identified. An infant at risk for inheriting the disorder can be tested prenatally or after birth, allowing for early diagnosis and treatment.

Research

Researchers at Johns Hopkins School of Medicine have been studying dyskeratosis congenita. They developed mice with a condition almost identical to the disorder to learn about how the lack of the protein telomerase (implicated in dyskeratosis congenita) contributes to the aging process and stem cell death. Stem cells in the bone marrow replenish the body's blood cells, including white cells for the immune system.

The researchers found that mice with just half the normal amount of telomerase had problems with stem cell growth and proliferation. The lack of telomerase caused the ends of chromosomes (telomeres) to shorten and stem cells to die early. The researchers are studying the affected stem cells to find out exactly how the short telomeres cause cell death. The research was reported in the December 16, 2005, issue of Cell.

Sources:

Hao, et al. "Short telomeres, even in the presence of telomerase, limit tissue renewal capacity." Cell 123(2005): 1121-1131.

"Dyskeratosis Congenita." Inherited Bone Marrow Failure Syndromes. National Cancer Institute. Jan 2006.

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