If you are born with sickle cell anaemia, it is usually diagnosed when you are a child as you start to show symptoms fairly early on. Sickle cell anaemia is an inherited disease; it is passed on from parent to child. If you have two faulty copies of the gene responsible, you will definitely experience sickle cell anaemia. If you only have one copy you are likely to be healthy, as the good gene compensates for the faulty one. You can, however, pass on the sickle cell anaemia gene to your children. If your partner also has the faulty gene, your child has a one in four chance having the disease.
Sickle cell screening is therefore very useful and it can be done. It can inform couples if they are at risk of passing on sickle cell anaemia, giving them the option of having sickle cell screening as part of genetic pre-implantation diagnosis to minimise the risk to their children.
This article on screening for sickle cell anaemia is by Kathryn Senior, a freelance journalist who writes health, medical, biological, and pharmaceutical articles for national and international journals, newsletters and web sites.
What is sickle cell anaemia?
Sickle cell anaemia is also known as sickle cell anaemia, sickle cell disease, or drepanocytosis. It is an inherited, lifelong disorder caused by a genetic mutation in the haemoglobin gene. This mutation causes normally round red blood cells to take on an uncharacteristic, rigid ‘sickle’ shape. The cells become stiff and sticky and they don’t move easily through blood vessels, sometimes getting stuck and forming clumps. This brings on a ‘sickling crisis’ typical of sickle cell anaemia that can be very painful. It can also lead to infections and organ damage, potentially causing serious complications such as stroke or blindness.
The red blood cells of someone with sickle cell anaemia do not live as long as normal red blood cells, usually only for about 10 to 20 days, compared with an average of 120 days for normal red blood cells. People with sickle cell anaemia therefore often have low numbers of red blood cells, which gives them ordinary anaemia. This can result in chronic tiredness, even without sickling crises.
How is this passed on?
Sickle cell anaemia is most common in people who descend from tropical and sub-tropical areas, such as sub-Saharan Africa, where malaria is or has been common. This is because people carrying one sickle cell anaemia gene are more resistant to malaria infection. People with Caribbean, Asian or Mediterranean ancestry are also considered ‘high risk’ for sickle cell anaemia.
Everyone carries two copies of the haemoglobin gene, one from each of their parents. When we have children of our own, we pass on one of these two genes. Inheriting two mutated genes results in sickle cell anaemia. Inheriting one sickle cell anaemia gene and one normal gene does not result in sickle cell disease, but instead is known as ‘sickle cell trait’. People with sickle cell trait do not usually experience symptoms of the disease unless under extreme physical conditions such as strenuous exercise, but are carriers and can pass sickle cell anaemia on to their own children. Unless you are already aware that you are a carrier of the sickle cell anaemia gene, the only way to find out is to undergo sickle cell screening.
Is the screening available to everyone?
Anyone can ask their doctor for a sickle cell screening test at any time. Sickle cell screening involves a simple blood test. In the UK, all pregnant women and newborn babies routinely undergo sickle cell screening. Couples planning to have children who think they may be carriers of sickle cell anemia may wish to ask their doctor for a sickle cell screening test before becoming pregnant, especially if one or both have family origins that put them at increased risk.
Can it be treated?
If you have sickle cell screening and the tests show you are carrying the sickle cell anaemia gene, you then face some difficult choices and it can help to understand what having sickle cell anaemia might mean. Although sickle cell anaemia is a chronic disease that people can live a normal lifespan with, the only cure is a bone marrow transplant. Due to difficulties in finding a suitable donor and the potential for serious side effects, this is not always suitable.
The symptoms of sickle cell anaemia can be treated and children who carry two faulty genes can learn how to prevent sickling crises. It can help to eat a diet rich in folic acid, vitamin D and zinc, or to take supplements. It is good to avoid smoking and drinking alcohol as both affect the condition of blood vessels. Vaccinations against infections such as flu, pneumococcal meningitis and Hepatitis B can also reduce the risk of a sickling crisis due to infection. For people with sickle cell anaemia who have very frequent sickle crises, regular blood transfusions can help to control symptoms.
Pre-implantation diagnosis for sickle cell anaemia is now available for couples having in vitro fertilisation treatment. If you have had sickle cell screening and know you are a carrier of the sickle cell gene, you may opt for IVF, even though you are able to conceive normally. On the third day of development, one cell is removed from the fertilised embryo produced by IVF. Sickle cell screening is done with other tests and, if one or two of the embryos are completely free of the sickle cell gene, they can be used to initiate pregnancy. This takes away any possibility that the baby will have sickle cell anaemia or be a carrier of the sickle cell trait.