Blood problems in newborn babies with Down's syndrome

Research in recent years has revealed that babies with Down syndrome usually have abnormalities in their blood when they are born. Many of these blood changes cause no problems at all and rapidly disappear. Other blood changes need special tests or treatment but have no long-term consequences. However, a small number of babies will have blood problems that can make them extremely unwell over their first few weeks of life.

There are two main reasons why blood abnormalities can lead to a serious problem in babies with Down syndrome.

The first is that about one in 10 babies will have a condition called Transient Leukaemia of Down Syndrome (some people call this "TAM" which is short for Transient Abnormal Myelopoiesis). And one in four of these babies can be seriously ill and need very specialised treatment to cure the problem. When diagnosed early, the cure rate is very high. And the treatment needed to cure the disease is usually very mild.

The second reason why it is important to identify blood problems in newborn babies with Down syndrome is because some children develop a special kind of leukaemia (Myeloid Leukaemia of Down Syndrome) that can only be cured by higher doses of chemotherapy. Altogether, somewhere between one in 100 and one in 50 of all children with Down syndrome develop this leukaemia before their fourth birthday.

But we now know that testing the blood at birth is the best way of identifying the children at risk of this leukaemia even though it doesn't develop until later on. And this means that the children at risk can be closely monitored at a blood clinic until the risk of leukaemia has passed (usually between the age of 2 and 4 years).

Of course, the only way to tell whether there is a serious blood problem is to check a blood sample. Most problems can be identified by doing a simple blood count and asking a blood specialist to look at the blood under the microscope. To do this, a tiny drop of blood is spread on a glass slide and mixed with coloured inks, which allow the different blood cell types to be identified. Although this is a simple test which does not cost much money, at the moment in the UK only some babies with Down syndrome have a routine blood count.

New national guidelines published this week in the British Journal of Haematology recommend that all babies with Down syndrome should have a blood count and blood film in the first few days of life. This test can be done at the same time as other blood tests and, in most cases, will mean that parents can be reassured.

In some cases the blood count or the blood film will alert the clinical team of a diagnosis of possible Transient Leukaemia of Down Syndrome. There is now a specific genetic test that can be done to identify Transient Leukaemia. This is called a GATA1 mutation test. It measures changes in the genetic code of the GATA1 gene.

The GATA1 mutation test also identifies all babies at risk of developing Myeloid Leukaemia of Down Syndrome in early childhood. It is not necessary to test all babies with Down syndrome using the GATA1 mutation test. At the moment the guidelines recommend that only babies where there is a very abnormal blood count or blood film should have this test.

This blog was written by Professor Irene Roberts, on behalf of the British Society of Haematology Transient Leukaemia of Down Syndrome Guidelines Group.

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