Темір жетіспеу анемиясы және сақиналы сидеробластар

Sideroblastic anemia, or sideroachrestic anemia, is a form of anemia in which the bone marrow produces ringed sideroblasts rather than healthy red blood cells (erythrocytes). In sideroblastic anemia, the body has iron available but cannot incorporate it into hemoglobin, which red blood cells need in order to transport oxygen efficiently. The disorder may be caused either by a genetic disorder or indirectly as part of myelodysplastic syndrome, which can develop into hematological malignancies (especially acute myeloid leukemia). Sideroblasts (sidero + blast) are nucleated erythroblasts (precursors to mature red blood cells) with granules of iron accumulated in the mitochondria surrounding the nucleus. Normally, sideroblasts are present in the bone marrow, and enter the circulation after maturing into a normal erythrocyte. The presence of sideroblasts per se does not define sideroblastic anemia. Only the finding of ring (or ringed) sideroblasts characterizes sideroblastic anemia. Ring sideroblasts are named so because iron laden mitochondria form a ring around the nucleus. It is a subtype of basophilic granules of the erythrocyte, but which can only be seen in bone marrow. To count a cell as a ring sideroblast, the ring must encircle a third or more of the nucleus and contain five or more iron granules, according to the 2008 WHO classification of the tumors of the hematopoietic and lymphoid tissues.

Symptoms of sideroblastic anemia include skin paleness, fatigue, dizziness, and enlarged spleen and liver. Heart disease, liver damage, and kidney failure can result from iron buildup in these organs. Symptoms of sideroblastic anemia usually resemble the common symptoms of anemia. In addition to the symptoms listed above, patients with sideroblastic anemia may experience shortness of breath, heart palpitations, and headache. Some patients may have bronze colored skin due to an overload of iron. Patients with syndromic hereditary sideroblastic anemia may experience diabetes mellitus and deafness.

Ringed sideroblasts are seen in the bone marrow. On the peripheral blood smear can be found erythrocytes with basophilic stippling (cytoplasmic granules of RNA precipitates) and Pappenheimer bodies (cytoplasmic granules of iron). The anemia is moderate to severe and dimorphic. Microscopic viewing of the red blood cells will reveal marked unequal cell size and abnormal cell shape. Basophilic stippling is marked and target cells are common. The mean cell volume is commonly decreased (i. e., a microcytic anemia), but it may also be normal or even high. The RDW is increased with the red blood cell histogram shifted to the left. Leukocytes and platelets are normal. Bone marrow shows erythroid hyperplasia with a maturation arrest. In excess of 40% of the developing erythrocytes are ringed sideroblasts. Serum iron, percentage saturation and ferritin are increased. The total iron binding capacity of the cells is normal to decreased. Stainable marrow hemosiderin is increased.

Occasionally, the anemia is so severe that support with transfusion is required. These patients usually do not respond to erythropoietin therapy. Some cases have been reported that the anemia is reversed or heme level is improved through use of moderate to high doses of pyridoxine (vitamin B6). In severe cases of SBA, bone marrow transplant is also an option with limited information about the success rate. Some cases are listed on MedLine and various other medical sites. In the case of isoniazid induced sideroblastic anemia, the addition of B6 is sufficient to correct the anemia. Deferoxamine, a chelating agent, is used to treat iron overload from transfusions. Therapeutic phlebotomy can be used to manage iron overload.

Sideroblastic anemias are often described as responsive or non responsive in terms of increased hemoglobin levels to pharmacological doses of vitamin B6. 1 Congenital: 80% are responsive, though the anemia does not completely resolve. 2 Acquired clonal: 40% are responsive, but the response may be minimal. 3 Acquired reversible: 60% are responsive, but course depends on treatment of the underlying cause. Severe refractory sideroblastic anemias requiring regular transfusions and/or that undergo leukemic transformation (5–10%) significantly reduce life expectancy.