Posted 7/1/2017 2:37 PM (GMT -6)
TPMT is an enzyme needed to metabolize imuran or 6mp. There are genes involved in production of this enzyme. A person may have the normal genes; or they may have mutations so that they produce only low levels of the enzyme; or they may have a mutation so that they don't produce the enzyme at all.
So this is a test that is usually ordered before a patient starts on imuran or 6mp.
If the person has the mutations where they don't produce the enzyme at all, giving imuran or 6mp to that person could be very dangerous.
If the person has partial ability to metabolize the drugs, they are not given or are given at low doses.
If the person has the normal genotype for metabolism of these drugs, they can be given at normal doses. That's still no guarantee that you won't have side effects, but it means your body will at least be able to metabolize the medication.