A stem cell or bone marrow transplant replaces damaged blood cells with healthy ones. It can be used to treat conditions affecting the blood cells, such as leukemia and lymphoma.

Stem cells are special cells produced by bone marrow (a spongy tissue found in the center of some bones) that can turn into different types of blood cells.

The 3 main types of blood cell they can become are:

• red blood cells – which carry oxygen around the body
• white blood cells – which help fight infection
• platelets – which help stop bleeding

A stem cell transplant involves destroying any unhealthy blood cells and replacing them with stem cells removed from the blood or bone marrow.

Why are stem cell transplants carried out?

Stem cell transplants are used to treat conditions in which the bone marrow is damaged and is no longer able to produce healthy blood cells.

Transplants can also be carried out to replace blood cells that are damaged or destroyed as a result of intensive cancer treatment.

Conditions that stem cell transplants can be used to treat include:

• Severe aplastic anemia (bone marrow failure)
• Leukemia – a type of cancer affecting white blood cells
• Lymphoma – another type of cancer affecting white blood cells
• Multiple myeloma – cancer affecting cells called plasma cells
• Certain blood, immune system and metabolic disorders – including sickle cell anemia, thalassaemia, severe combined immunodeficiency (SCID) and Hurler syndrome

A stem cell transplant will usually only be carried out if other treatments have not helped, the potential benefits of a transplant outweigh the risks and you’re in relatively good health, despite your underlying condition.

What does a stem cell transplant involve?

A stem cell transplant can involve taking healthy stem cells from the blood or bone marrow of one person – ideally a close family member with the same or similar tissue type – and transferring them to another person. This is called an allogeneic transplant.

It’s also possible to remove stem cells from your own body and transplant them later, after any damaged or diseased cells have been removed. This is called an autologous transplant.

A stem cell transplant has 5 main stages. These are:

1. Tests and examinations – to assess your general level of health.
2. Harvesting – the process of collecting the stem cells to be used in the transplant, either from you or a donor.
3. Conditioning – treatment with chemotherapy and/or radiotherapyto prepare your body for the transplant.
4. Transplanting the stem cells.
5. Recovery – you’ll need to stay in the hospital for at least a few weeks until the transplant starts to take effect.

Having a stem cell transplant can be an intensive and challenging experience. You’ll usually need to stay in hospital for at least a few weeks until the transplant starts to take effect and it can take up to a year or longer to fully recover.