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.
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.
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.
