What is being tested?Thiopurine drugs suppress the immune system and are used to treat patients after
organ transplants and in the treatment of a wide range of diseases such as leukaemia, inflammatory bowel disease and skin disorders such as
eczema. The most commonly used thiopurine drug is called azathioprine.
1 person in every 300 lacks thiopurine s-methyltransferase (TPMT) which is an enzyme which helps remove thiopurine drugs such as azathioprine from the body. Individuals with no TPMT enzyme can become severely ill if treated with normal doses of thiopurine drugs. These patients develop bone marrow suppression with a reduction in blood cells, which causes
anaemia, infection and abnormal bleeding. Such side effects can be avoided if TPMT is measured before starting treatment.
