Sideroblastic anemia is a blood disorder in which the red blood cells fail to develop normally, resulting in the formation of what are known as ring sideroblasts in the bone marrow, together with general symptoms of anemia, such as fatigue and pale skin. A ring, or ringed, sideroblast is an immature red blood cell with a ring of iron around the nucleus. Sideroblastic anemia is associated with a number of different diseases and may be inherited, so that a person is born with the condition, or it can be acquired later in life. It may be part of a myelodysplastic syndrome, where blood cell production in the bone marrow becomes abnormal with the risk that it may develop into leukemia, or cancer of the blood and bone marrow. Drugs are a common cause of sideroblastic anemia, particularly alcohol, as are certain antibiotics, chemotherapy treatments and heavy metals such as lead.
Hemoglobin, the molecule that binds oxygen inside a red blood cell, consists of a globin portion, made up of proteins, and a heme portion, which normally contains iron. In sideroblastic anemia, the immature red blood cells in the bone marrow fail to take up iron properly into the heme part of hemoglobin, with the result that iron is deposited in the substance of the cell, characteristically forming a ring around the nucleus. This is known as a sideroblastic ring and the cells are referred to as ring, or ringed, sideroblasts.
The majority of cases of sideroblastic anemia are acquired rather than inherited, with alcohol abuse being the most common cause overall. Other causes include drugs such as isoniazid, used in the treatment of tuberculosis, deficiencies of copper and vitamin B6, and lead or zinc poisoning, as well as the myelodysplastic syndromes and other bone marrow diseases. Inherited forms of the condition are more common in men, and in mild cases it can remain undetected until the age of around 40 or over.
Sideroblastic anemia can be diagnosed by looking at the bone marrow under a microscope, where ring sideroblasts can be seen. Some of the cells from the general circulation will usually appear pale, lacking the typical red color associated with normal amounts of hemoglobin. In the hereditary forms of the anemia, the cells may also be smaller than usual.
Inherited sideroblastic anemia can sometimes be treated with vitamin B6, with the treatment being taken for life if the disease responds. While some of the causes of acquired sideroblastic anemia can be reversed, such as certain antibiotics being replaced by others or the consumption of alcohol being stopped, this is not always possible. Treatment with vitamin B6 can also work in some cases of the acquired anemia, and sometimes a blood transfusion may be carried out.