When a child carries a sickle cell trait

Last week, we tackled sickle cell, the disease; this week, I will look at the trait. Sickle cell trait refers to a condition in which a person has one abnormal allele of the haemoglobin beta gene, but does not display the severe symptoms of sickle cell disease that occurs in a person who has two copies of that allele. Normal haemoglobin is called haemoglobin A. People with sickle cell disease have only haemoglobin S, which turns normal, round red blood cells into abnormally curved (sickle) shapes.

Normally, a person inherits two copies of the gene that produces beta-globin, a protein needed to produce normal haemoglobin (ha emoglobin A, genotype AA).

 If your child has the sickle cell trait, he does not show any signs of sickle cell disease, and is a carrier for sickle cell gene (allele).  Normally, adult humans have Haemoglobin A (considered AA); those with the trait have AS, while sicklers have SS. If your spouse, too, is AS then some of your children (25 per cent) can become sicklers, 50 per cent will be AS like you while the rest (25 per cent) would be normal (AA).

 If one parent has sickle-cell anaemia (SS) and the other has sickle-cell trait, then there is a 50 per cent chance of a child having sickle-cell disease, and a 50 per cent chance of a child having sickle-cell trait. When both parents have sickle-cell trait, a child has a 25 per cent chance of sickle-cell disease. You can find out if your partner, yourself or your child has sickle cell disease or is a carrier by having the haemoglobin electrophoresis test performed on your blood. Sickle cell trait provides a survival advantage over people with normal hemoglobin in regions where malaria is endemic.

The trait is known to cause significantly fewer deaths due to malaria, especially when Plasmodium falciparum is the causative organism. Because of the unique survival advantage, people with the trait increase in number as more people infected with malaria and having the normal haemoglobin, tend to succumb to the complications.

In some cases, athletes with sickle cell trait do not achieve the same level of performance as elite athletes with normal haemoglobin AA. Athletes with sickle cell trait and their instructors must be aware of the dangers of the condition during anaerobic exertion, especially in hot and dehydrated conditions.

Photo: www.research.chop.edu