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Wednesday, February 8, 2012
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NetWellness provides the highest quality health information and education services created and evaluated by faculty of our partner universities.
Wednesday, February 8, 2012
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Inherited Disorders and Birth Defects |
Hemoglobinopathies-F Texas08/08/2001 |
My daughter, now 3 months old, was found to have a hemoglobinopathy during a routine MN newborn screen. After more testing and waiting, we were told that there was an abnormality in her fetal hemoglobin- more specifically a gamma chain variant that is called F Texas. Can you tell me more about this disorder ie..what to expect, how it was inheritated (are my husband and I both carriers or could one of us had the disease and not known it because our generation wasn`t tested for hemoglobinopathies) and does it have any relation to our son who was born 3 1/2 years ago with left radial ray aplasia? Thank You!
Hemoglobin is a protein in red blood cells that transports oxygen from the lungs to the tissues of the body. In normal adults, the structure of hemoglobin (Hb) is a tetramer composed of two alpha and two beta globin polypeptide chains.During development, the embryo and fetus have different Hb chains present in order to meet their oxygenation needs. The two major chains are alpha and gamma (Hb F) and a small amount of beta chains. During the 3rd trimester, the gamma chains start to lessen and the beta chains replace them. At about 6 months of age, a baby usually has less than 2% of gamma chains - or what is called fetal hemoglobin (Hb F).
When there is a mutation (change) in one of the base pairs in a gene - it results in a different amino acid being produced in one of the chains. This change may have no effect or it may alter such things as oxygen affinity - how well the molecule holds onto oxygen or its solubility or stability.
More than 700 inherited hemoglobin variants have been identified. Mutations that cause major disease are those that usually involve the alpha chains or beta chains - leading to disorders such as sickle cell disease or one of the thalassemias. These disorders are usually inherited as autosomal recessive disorders - where parents are normal but carry the mutation in one of their genes. When the parents both pass the mutated gene at the same time to an offspring, the baby gets two abnormal genes - and has the disorder.
Hemoglobin F variants (such as the one you describe - Texas variant) may not cause any major health problems unless they are associated with one of the thalassemias or sickle cell disorders.
You have asked excellent questions regarding inheritance, prognosis and management. The hemoglobinopathies are complex. I would highly recommend that you talk to your doctor and ask to be referred to a geneticist or genetic counselor who can answer your questions in detail. The website below will assist you in locating a genetics center near you. Also, the question of the radial aplasia in your son can also be addressed at that time. I would not think it is related but can not say that for certain.
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Anne Matthews, RN, PhD Associate Professor of Genetics Department of Genetics School of Medicine Case Western Reserve University |
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