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Saturday, 12 April 2014

An Understanding Of Sickle Cell Anemia Prevention

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By Anita Ortega


Sickle Cell Disease is an inherited disorder of red blood cells, called erythrocytes, and the most common genetic disease in the United States. Normal red blood cells are round and concave in the middle; they flow easily through the bloodstream. Diseased erythrocytes, on the other hand, are sticky and bent into a sickle shape, like the sharp implements that are used to cut through sugar cane. Sickle cell anemia prevention is best discussed with a genetic counselor.

In order for a child to develop SCA, both parents must carry the trait for sickle cell hemoglobin (Type AS). If so, there is a 50% chance that the offspring will carry the trait and a 25% chance that it will either carry the trait or not. On the other hand, if one parent has the AS trait and the other has normal hemoglobin (Type AA), then there is a 50% chance that their children will carry the trait but they will not inherit the disease.

People who come from warm climates are more likely to be affected by SCA. It affects people of American African origin the most, with one in ten newborns carrying the AS trait and one in roughly 450 deliveries resulting in an infant with the disease. Hispanic newborns are half as likely to develop the trait and the disease. Other nationalities that are affected are people from Asiatic India, the Arab countries, Greece, Italy and Latin America.

If the gene for this disease is recessive, which it is, how did it get spread so widely through certain populations? This is because people who carry the trait have a tolerance to malaria, a deadly parasitic disease transmitted by mosquito bites in certain regions of the world. For a long time, the reason why people who have a selective advantage was unknown.

In 2011, a paper was published in the prestigious scientific journal, Cell, that shed light on the molecular mechanisms underlying this curious situation. While this is great news for that half of the world for which malaria is a menace, it does little to comfort those who suffer from SCA.

A lot of the symptoms and signs of SCD are common to other forms of anemia. These include dizziness, headaches, extreme fatigue, shortness of breath, pale skin, jaundiced eyes and coldness in the extremities. The condition is also characterized by sudden episodes of debilitating pain throughout the entire body.

A sickle cell crisis also affects the major organs (lungs, liver and kidneys). This, and the widespread pain in the limbs, is caused when the oddly-shaped blood cells block blood flow, causing pain and organ damage. The pain may last for several hours or persist for a week or longer.

Today, all neonates in the USA are tested for AS at birth. This allows early access to treatment. For now, the only way to prevent SCA is for prospective parents to be tested for the trait and discuss the results with a genetic counselor. A genetic counselor is trained to discuss the options the would-be parents have, given the results of the blood tests.




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