Azathioprine and mercaptopurine (MP) are well established treatments for inflammatory bowel disease (IBD).
However, some patients experience severe adverse effects to these treatments.
It is possible that the likelihood and type of adverse events may relate to thiopurine methyltransferase (TPMT) enzyme activity and genotype.
In this study, researchers from New Zealand compared the frequency of TPMT genotypes in IBD patients who had severe adverse reactions to azathioprine or MP, with those who did not.
The team of physicians identified all patients with IBD who had been treated with azathioprine or MP in Christchurch between 1996 and 2002.
|"Most patients with reactions did not have gene mutations".|
|Alimentary Pharmacology and Therapeutics|
They invited all patients to provide a peripheral blood sample for analysis of TPMT genotype.
The team then compared the genotype frequencies between the 2 groups.
The doctors identified 56 with adverse effects which required the cessation of therapy. Of these, 50 were genotyped.
They found that the reactions included allergic-type (25%), hepatitis (33%), nausea/vomiting (14%), bone marrow suppression (10%), pancreatitis (6%) and other (12%).
The team determined that 10% of patients with reactions had the TPMT genotype *1/*3. A further 2% had the *3/*3 genotype, while the rest had the wildtype genotype *1/*1.
The individual with the *3/*3 genotype had severe pancytopenia and required hospitalization.
In the control group, 6% had the *1/*3 genotype, while the rest were *1/*1.
Dr Gearry's team concluded, "The TPMT allele frequency in our population with inflammatory bowel disease is similar to that reported elsewhere".
"There was a slight trend for more frequent TPMT mutations in the patients with adverse reactions, but this was not statistically significant".
"Most patients with reactions did not have gene mutations".