Will I pass on thalassaemia alpha to my children?
Q: I have been diagnosed for thalassaemia alpha 3. I am 12 weeks pregnant and am carrying twins. My husband's blood tests showed an MCV of 86.91 fl. His Hb was 13.89 gms%, RBC count was 5.02 mill/cmm, MCH was 27.65 pg. What is the risk to my babies of being carriers or suffering from full blown Thalassaemia?
A:Alpha thalassaemia occurs when one or more of the four alpha chain genes fails to function causing deficient or absent production of alpha-globin synthesis. Each individual carries 4 "a" genes, 2 from the father and 2 from the mother. This results in 4 possible genotypes, each resulting in a different clinical syndrome. Genotype Clinical state a-/aa Silent carrier or mild alpha thalassaemia minor; alpha+ thalassaemia trait a-/a- or --/a a Homozygous alpha+ thalassaemia or --/a a alpha0 thalassaemia trait a-/-- Hemoglobin H disease --/-- Hydrops fetalis or homozygous alpha thalassaemia; Barts hemoglobin The loss of one gene diminishes the production of the alpha protein only slightly. This condition is so close to normal that it can be detected only by specialised laboratory techniques and a person with this condition is called a silent carrier because of the difficulty in detection. The loss of two genes (two-gene deletion alpha thalassaemia) produces a condition with small red blood cells, and at most a mild anaemia. People with this condition look and feel normal. The condition can, however, be detected by routine blood testing. The loss of three alpha genes produces a serious haematological problem (three-gene deletion alpha thalassaemia). Patients suffer from severe anaemia, and often require blood transfusions to survive. The severe imbalance between the alpha chain and beta chain production causes an accumulation of beta chains inside the red blood cells producing an abnormal haemoglobin, called haemoglobin H . The condition is called haemoglobin H disease. Haemoglobin H causes two problems - first it does not carry oxygen properly, making it functionally useless to the cell and secondly it damages the red cell, accelerating cell destruction. The combination of the very low production of alpha chains and destruction of red cells in haemoglobin H disease produces a severe, life-threatening anaemia. Untreated, most patients die in childhood or early adolescence. The loss of all four alpha genes produces a condition that is incompatible with life. Most people with four-gene deletion alpha thalassaemia die in utero or shortly after birth. People of Asian ancestry often have two alpha globin genes deleted on the same chromosome 16. The parents each have the mild thalassaemia that results with two functioning alpha globin genes. The offspring that inherits the double deletion from one parent and the single from the other will have Haemoglobin H disease while the offspring who inherits no alpha genes from the parents dies in utero. People of African ancestry usually have only one alpha globin gene deleted per chromosome. The parents each have the mild thalassaemia that results with two functioning alpha globin genes. The offspring can, at most, inherit the relatively mild condition of the parents. Your husbands CBC does not suggest a thalassaemia trait but both of you need to consult a haematologist who will be able to advise you appropriately as alpha thalassaemia trait (one or two gene deletion alpha thalassaemia) can only be ascertained by a specialised DNA analysis.