Dyskeratosis congenita


Dyskeratosis congenita

Description, Causes and Risk Factors:

Abbreviation: DC.

Dyskeratosis congenita is a severe, multisystem bone marrow failure syndrome, with associated cutaneous and noncutaneous abnormalities. The triad of abnormal skin pigmentation, nail dystrophy and mucosal leukoplakia characterize dyskeratosis congenita. Other findings include learning difficulties or mild-to-moderate mental retardation, short stature, underdeveloped or undescended testes, and abnormal bone trabeculation or osteoporosis.

Dyskeratosis congenita is a rare syndrome, with approximately less than 200 individuals reported in the literature, with 90% of patients being male.

Dyskeratosis congenita

The candidate-gene region for X-linked dyskeratosis congenita was originally mapped to Xq28 and was further refined to a 1.4-Mb region in the distal end of Xq28. The DKC1 gene was subsequently positionally cloned as the result of the identification of a partial gene deletion in one male dyskeratosis congenita patient.

The gene responsible for the X-linked form of the disease encodes a protein involved in ribosome biogenesis and in stabilizing the telomerase complex, while the autosomal dominant form is caused by mutations in the core RNA component of telomerase. It has been suggested that dyskeratosis congenita is primarily a disease of defective telomere maintenance. Premature shortening of telomeres resulting in a limited proliferative potential of stem cells would explain the pathology observed in dyskeratosis congenita, as the affected tissues are those that require constant renewal.

It mainly occurs in the males, inherited as X-linked recessive disorder with male:female predilection of 13:1. Occurrence in extremely low percentage of the females suggests that there are subsets inherited in an autosomal dominant fashion. Autosomal dominant form of dyskeratosis congenita is associated with mutations in the RNA component of telomerase, hTERC, while X-linked dyskeratosis congenita is due to mutations in the gene encoding dyskerin, a protein implicated in both telomerase function and RNA processing. In DC multiple organ systems are affected due to pleiotropic mutation in the gene.

Symptoms:

People were diagnosed with the disease if they had three main symptoms:

    A lacy-looking rash on the face, neck and chest.

  • White patches in the mouth (leukoplakia).

  • Fingernails and toenails that are not shaped normally.

  • Bone marrow failure.

  • Skin abnormalities.

  • Lung complications.

The symptoms may be severe or mild.

Diagnosis:

The differential diagnosis includes Fanconi's anaemia, pachyonychia congenital, white spongy nevus and GVHD (graft versushost disease).

DC can be definitively diagnosed in most cases by genetic testing.

There are a couple of ways to test for it: the patient can either submit a blood sample or have his mouth swabbed for cells to be tested. Testing is available through the DC registry and through a company called GeneDx. In certain cases the results of this testing have been negative even when the disease is present; in these cases, diagnosis must be made via identification of symptoms.

Treatment:

There is no effective and curative treatment for dyskeratosis congenita. Some interceptive and preventive measures can be adopted for which an early diagnosis is essential. Patient should be kept under observation and recalled for periodic follow up. In follow-up visits biopsy and complete blood picture should be advised to detect any malignant changes in white patches or developing hematopoietic disorder. Chemotherapy with bleomycin or cyclophosphamide is effective for treating leukoplakia associated with dyskeratosis congenita. Researchers reported that a vitamin A derivative, etretinate is effective for treating leukoplakia in dyskeratosis congenita. However side effects like exfoliative cheilitis, angular cheilitis and teratogenicity can occur. Excisional biopsy can also be indicated to eliminate the possibility of development of carcinoma in leukoplakic areas. For extensive lesions in which surgery is not possible administration of steroids and testosterone can be used. In future gene therapy can provide an alternative therapy for management of this fatal condition.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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