Bone marrow transplants are often needed when a person's own bone marrow has been damaged and can no longer produce normal blood cells.

Disruption to the production of blood cells can be very serious, particularly if you:

• don't have enough red blood cells – your body will be starved of oxygen, you'll feel tired and faint and your organs could be damaged
• don't have enough white blood cells – your risk of developing a serious infection will be significantly increased  
• don't have enough platelets – you'll bleed and bruise more easily

Some of the conditions that can affect blood and bone marrow are described below.

Bone marrow failure

The continuous production of blood cells and platelets to replace old cells is essential for a healthy life.

In adults, this reproduction process only occurs within bone marrow. Therefore, a bone marrow transplant may be needed if your bone marrow fails (known as severe aplastic anaemia).

This may happen as a consequence of an inherited condition – a rare type of anaemia, for example. It could also be the result of an acquired condition, including rare complications of certain infections, such as hepatitis B, Epstein-Barr virus (which causes glandular fever) or parvovirus B19.

Leukaemia

Leukaemia is cancer of the white blood cells. The white blood cells replicate in an uncontrollable manner and don't develop any infection-fighting properties.

The cancerous cells can quickly spread through your bloodstream, leading to a lack of room for red blood cells and platelets.

This can lead to the symptoms of anaemia and increases your risk of serious infection. You'll also bleed and bruise more easily.

There are numerous types of leukaemia where a bone marrow transplant may be needed. These are:

• acute lymphoblastic leukaemia
• acute myeloid leukaemia
• chronic lymphocytic leukaemia
• chronic myeloid leukaemia 

Non-Hodgkin lymphoma

Non-Hodgkin lymphoma is another cancer of the white blood cells. However, unlike leukaemia, it spreads through the lymphatic system, rather than the bloodstream.

The lymphatic system is a series of connected glands (nodes) that are located around your body. It's an important part of the immune system, which is your body's natural defence against infection and illness.

Read more about non-Hodgkin lymphoma.

Genetic blood and immune system disorders

There are number of blood disorders where mutations (alterations) in your genes cause the blood cells to develop abnormally.

These include sickle cell anaemia and thalassaemia. Both conditions interfere with the production of red blood cells.

Immune system disorders can include a wide range of immunodeficiencies and some other genetic conditions.