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An over-production of platelets.


Shortage of platelets, leading to problems with bleeding.


When blood clots form in a blood vessel, usually in a vein but sometimes in an artery. It is potentially life-threatening if left untreated.


A gland at the base of the neck which is part of the immune system. T cells are produced in the bone marrow but they cannot work as part of the immune system until they have passed through the thymus.

T Cell T lymphocyte

A type of white blood cell which matures in the thymus (hence T cells). It is involved in controlling immune reactions and in fighting viral infections. Uncontrolled production of this type of cell gives rise to T-cell leukaemia/lymphoma.

Total body irradiation

Radiotherapy often given in several doses before bone marrow transplantation. The aim is to kill any remaining abnormal cells in the patient. It also “clears” a space where in the bone marrow for the new marrow to occupy. It is used along with high does anti-cancer drugs. The hospital team will discuss the procedure and its side-effects individually with the patient.


The change of normal cell into a cancerous cell, or the acceleration of chronic myeloid leukaemia to a more acute phase with the production of large numbers of blast cells.


A chromosome abnormality in which the part of one chromosome has become transferred to another.

Trephine biopsy

Taking out a small piece of bone marrow under local anaesthetic. Unlike a bone marrow aspirate this includes bone and can be used to assess bone marrow structure, the number and distribution of all the blood cell types. The trephine biopsy is normally done at the same time as a bone marrow aspirate.


There are normally two copies of each chromosome – one inherited from each parent. When there are three copies of a chromosome present, this is called trisomy. One example of a condition caused by trisomy is Down syndrome. Leukaemia cells may have trisomy present even when other cells in the body are normal.


A mass of abnormal cells which may be benign or malignant.

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