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Disorders of Iron
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Search by Disorder
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| Iron Related Issues
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| Sideroblastic Anemia
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Sideroblastic anemia is an enzyme disorder in which the body has adequate iron but is unable to incorporate it into hemoglobin. Iron enters the developing red blood cell (erythroblasts); here iron accumulates in the mitochondria giving a ringed appearance to the nucleus (ringed sideroblast). The mitochondria are overloaded with iron and hemoglobin production (heme synthesis) is defective. Sideroblasts are visible with Prussian blue staining and observable under microscopic examination of bone marrow. Because these ringed sideroblasts can develop poorly or not at all into mature red cells, anemia is the consequence.
Sideroblastic anemia (SA) is a complicated disorder and therefore difficult to treat. . Often SA acts like iron deficiency anemia (IDA), but unlike IDA, iron tests are normal or increased with SA.
Three categories of sideroblastic anemia are: hereditary, acquired or idiopathic.
Hereditary Sideroblastic Anemia is due to a genetic defect; the gene is an X-linked recessive (not dominant) gene. It may manifest in both men and women but is seen more commonly in young males, maternal uncles and cousins. Hereditary sideroblastic anemia generally manifests during the first three decades of life especially during adolescence but it has been diagnosed in patients over seventy.
Acquired sideroblastic anemia is due to prolonged exposure to toxins like alcohol, lead, drugs or nutritional imbalances such as deficiency in folic acid, deficiency in copper or excess zinc. Other causes are due to disease such as inflammatory conditions like rheumatoid arthritis, cancerous conditions such as leukemia, lymphoma; kidney disorders causing uremia; endocrine disorders such as hyperthyroidism; metabolic disorders such as porphyria cutanea tarda. Acquired SA is usually seen in patients over 65 year of age but it can be present as early as mid to late fifties.
Idiopathic means the cause is unknown; this category of SA is referred to as myelodysplastic syndrome (MDS). Myelodysplasia is a bone marrow dysfunction disorder which can develop into aplastic anemia requiring bone marrow or stem cell transplantation. Lab findings for acquired/idiopathic sideroblastic anemia: Anemia is usually mild with hemoglobin 10-11.8g/dL Serum iron increased, transferrin iron saturation percentage increased, ferritin increased, transferrin is decreased. TIBC is normal to decreased; serum transferrin receptor is normal to high Mean Corpuscular Volume (MCV) is normal to slightly increased. Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC) are usually normal. Red Cell Distribution Width (RDW) is increased. White blood cells and platelets are decreased.
Symptoms might include enlarged spleen or liver, liver disease, cardiac arrhythmia along with the following specific lab findings:
Treatment depends on the cause; if acquired, remove the offending agent and anemia may disappear. With inflammatory disease such as rheumatoid arthritis, the underlying condition should be treated.
In cases of extreme anemia, whole red blood cell transfusion may be required. Pyridoxine (vitamin B6) 50 to 200mgs taken daily may reverse anemia. Cases of hereditary, acquired and idiopathic anemia have responded to pyridoxine therapy. Pregnant or nursing mothers may wish to limit B6 to 100mg (milligrams) daily, then resume higher B6 dosage.
Iron overload accompanies sideroblastic anemia. Repeated whole red blood cell transfusion will contribute significantly to this exsisting iron burden and likely require chelation therapy with desferrioxamine (Desferal).
Desferal (desferrioxamine) is a drug with iron chelating properties. Desferal binds excess body iron and promotes excretion by the liver and kidneys in urine and bile in feces. It is administered subcutaneously (beneath the skin) by intravenous infusion from a small portable pump.
A patient wears the pump 9-12 hours each day, usually at night while sleeping. The procedure is fairly expensive. Side effects can be varied including pain and swelling at injection site.
Alcohol and certain drugs can be associated with acquired sideroblastic anemia: progesterone like those found in oral contraceptives and in hormone replacement therapy, copper chelating drugs like trientine-used in treatment of Wilson's (excess copper) disease, anti-tuberculosis drugs like isoniazid (type of antibiotic), penicillamine trade name Cuprimine used for extreme arthritic conditions, Wilson's disease and excessive ingestion of zinc.
Leukemia such as acute granulocytic leukemia can develop as a result of acquired sideroblastic anemia. Myelodysplasic syndromes (MDS) are generally observed in the early pre-leukemic stages of disease. More information about MDS or leukemia may be found in the resources section for this topic.
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