What Is Chromosomal Breakage Syndromes In Genetics

Chromosomal Breakage Syndromes is very important topic.There are many causes have been discovered about inherited chromosome breakage.we will discuss about that in this article.

Bloom’s Syndrome

This disease is character­ized by congenital telangiectatic erythema appear­ing primarily in the butterfly region of the face, other regions of the head, forearms, and dorsa of the hands. Sun sensitivity is common, and the erythema abates with protection from sunlight. Low birth .weight, microcephaly, and stunted growth are universal features of the syndrome. Few patients live beyond the age of 20, and the incidence of leukemia and other malignancies is unusually high.Bloom’s syndrome is caused by homozygosity for an autosomal recessive gene.

What Is Chromosomal Breakage Syndromes In Genetics

Consanguinity between parents of affected children, high inci­dence among Jews, and frequent occurrence Of affected sibs attest to the genetic cause of the dis­ease. Multiple chromosome breaks and structural abnormalities are commonly found in skin fibro­blasts as well as cultured lymphocytes. In addition to breaks and gaps, dicentric chromosomes, acentric fragments, and chromatid exchanges occur. Parents of affected children may also ex­hibit a moderate increase in chromosome breakage.

Here Is Complete Guide About Chromosomal Breakage Syndromes, You Must Know

Fanconi’s Anemia.

Pancytopenia caused by bone marrow hypoplasia is the cardinal sign of this disease. There is a high incidence of congeni­tal anomalies, particularly of the skeletal and uro­genital systems. Growth retardation is accom­panied by microcephaly, although the intellect is usually normal. Hyperpigmentation of the neck, abdomen, axillae, and groin occurs.What Is Chromosomal Breakage Syndromes In Genetics

Fanconi’s anemia is an autosomal recessive disease. It is usually fatal in childhood or early adulthood from complications of the hematologic defen such as. hemorrhage or infection. There is an increased risk of leukemia and other malig­nancies. The basic genetic defect is unknown, al­though a disturbance in hexokinase metabolism has been reported.

A tendency to increased chromosome breakage and rearrangement is similar to that in Bloom’s syndrome. Th<_ chromosomal lesions are found in cultured lymphocytes, direct bone marrow prepar­ations, and skin fibroblasts. Cells cultured from patients with both diseases are particularly sus­ceptible to transformation by the SV40 virus.

Other Hematologic Syndromes.

Several other conditions with bone marrow hypoplasia, dysgammaglobulinemia, telangiectasia, and/or congenital anomalies have been suspected of having chromo­somal lesions similar to those reported in Bloom’s syndrome and Fanconi’s anemia. These include ataxia-telangiectasia, Blackfan-Diamond syn­drome, multiple myeloma, Wiskott-Aldrich syn­drome, and Rothmund-Thomson syndrome. Cyto­genetic reports of these conditions are inconsistent, however, and definite conclusions await further evidence.

Familial Specific Chromosomal Breakage.

Re­cently several “families have been described in which a specific region of a specific chromosome is particularly susceptible to attenuation and breakage. These patients do not have a patho­gnomonic phenotype. In fact the condition may oc­cur in healthy, fertile adults.

Four families have been described in which the lesion occurs in the proximal long arm of chromo­some No. 2. Other families exhibit a tendency to breakage in the distal long arm of No. 16 or one of the members of the 6-12 group. Pedigree analysis indicates a typical autosomal dominant pattern. The cause of the defect is unknown, but a curious disturbance of replication occurs in the abnormal chromosome. The segment distal to the site of breakage may undergo endoreduplication, whereas the remainder of the chromosomal complement is normal.

 

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