Myelodysplastic syndromes (MDS) are a group of blood disorders where the balance of healthy blood cells in the body is disrupted.

MDS are sometimes called bone marrow disorders, as it is within the bone marrow - the soft tissue in the middle of our bones, where all our blood cells are made - that these conditions originate.

When people have MDS normal blood cell production breaks down. Usually, the bone marrow is over-active and makes far too many blood cells. But these blood cells are mostly defective and not able to do their jobs properly. Many of them are destroyed before entering the blood stream. For this reason people with MDS have a low blood count, with far too few cells in their blood.

There are three main types of blood cell, any or all of which may be affected by MDS. The first are red blood cells, which are responsible for carrying oxygen around the body. The second are white blood cells, which are an important part of our immune system that fights infection. And the third are platelets, which clot the blood and stop us from bleeding and bruising easily.

There are many different types of MDS, all with slightly different features. In a few cases, MDS develops into a form of leukaemia, usually acute myeloid leukaemia (AML).

What are the signs and symptoms?