Instituto Valenciano de Microbiología
(IVAMI)

Masía El Romeral
Ctra. de Bétera a San Antonio Km. 0.3
46117 Bétera (Valencia)
Phone. 96 169 17 02
Fax 96 169 16 37
Email: 
www.ivami.com
CIF B-96337217

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X - linked sideroblastic anemia and ataxia (X-linked sideroblastic anemia and ataxia) - Gen ABCB7

Sideroblastic anemia and ataxia linked to the X chromosome, is a rare disease characterized by sideroblastic anemia and ataxia, which affects only males. Sideroblastic anemia is the result of erythroblasts, during development of erythrocytes do not produce enough hemoglobin, the protein that carries oxygen in the blood. Siderobl√°stica people with X - linked anemia and ataxia have mature and hypochromic microcytic cells due to deficiency of hemoglobin. This process also leads to an abnormal accumulation of iron in red blood cells. Erythroblasts charged iron present in the bone marrow, are called sideroblasts.

Unlike other forms of sideroblastic anemia, sideroblastic anemia X - linked ataxia not cause a potentially dangerous accumulation of iron in the body. The anemia is usually mild and usually does not cause any symptoms. In this process, as well as sideroblastic anemia, ataxia exists, with consequent problems of balance and motor coordination appear to occur early in life. Ataxia affects mainly l trunk, so it's hard to sit, stand and walk unassisted. In addition to ataxia, people with this condition often present with dismetría and disdiadocoquinesis. In addition, some affected individuals suffer from dysarthria, tremors and abnormal eye movements.

This process is due to mutations in the gene ABCB7, located on the long arm of the X chromosome (Xq13.3), encoding a protein essential for the production of heme, a protein component of hemoglobin, vital for the supply oxygen throughout the body. The ABCB7 protein also plays a role in the formation of certain proteins containing groups and sulfur atoms iron. It is believed that the protein ABCB7 helps maintain iron homeostasis in the development of erythrocytes.

They have identified at least three mutations in the gene ABCB7 in people with sideroblastic anemia X - linked and ataxia. Each of these mutations change a single amino acid in the protein ABCB7, which slightly alters its structure. As a result, the protein can not perform their usual function in the production of heme and iron homeostasis. Anemia occurs when the heme can not be produced normally, and thus sufficient hemoglobin occurs. It is unclear how changes in the ABCB7 gene results in ataxia and other abnormal movements.

This disease is inherited in a recessive X - linked pattern in males, who have only one X chromosome, an altered copy of the gene in each cell it is sufficient to express the disease. In females, having two X chromosomes, the mutation should occur in both copies of the gene for the disease is expressed. Because it is unlikely that women have two altered copies of this gene, males are more affected than women. A feature of the X - linked inheritance is that fathers can not pass on to their children the traits linked to chromosome X. In X - linked recessive inheritance, a woman with an altered copy of the gene in each cell is called a carrier. The carriers of a mutation ABCB7 can transmit the mutated gene, but do not have problems associated with ataxia linked sideroblastic anemia X. However, the carriers may have hypochromic microcytic and erythrocytes.

           

Tests in IVAMI: in IVAMI perform detection of mutations associated with X - linked sideroblastic anemia and ataxia, using the complete PCR amplification of exons ABCB7 gene, and subsequent sequencing.

Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).