Question 2 - Allopurinol and azathioprine

Mr Lee is a 42-year-old Chinese with a history of Crohn’s disease. He experienced disease flair recently upon tapering of budesonide. Therefore, his physician-in -charge decided to prescribe azathioprine to improve the control of his disease. However he was worried about the potential side-effects of azathioprine, in particular myelosuppression.

a) What genetic test can help to predict the risk of myelosuppression associated with azathioprine? (1 mark)

b) Please explain the pathophysiology of myelosuppression associated with azathioprine? (3 marks)

c) How to interpret the results of this genetic test? (6 marks)

d) If the genetic test is not available in your hospital what is the alternative test that can predict the risk of myelosuppression associated with azathioprine? (1 mark)

Mr Lee was diagnosed to have gout arthritis recently. Since he had two attacks in the last six months, his physician-in-charge decided to prescribe allopurinol for him to lower his serum urate level.

e) What is genetic test can be considered for patients before prescribing allopurinol (1 mark)

f) Name TWO adverse drug reactions of allopurinol that can be prevented by this genetic tests (2 marks)

g) If the test is positive what is your recommendation regarding the long-term management of gouty arthritis (2 marks)

h) What precautions should you recommend to Mr Lee if allopurinol is prescribed while he is receiving azathioprine? Please explain. (4 marks)

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