The Examination of a TPMT Gene Before Administration of Azathioprine in Rheumatology Practice and Identification of a Novel Variant p.W29R.

Abstract

Two-hundred patients were assessed for the presence of genetic allelic variants using PCR amplification and direct sequencing. In 19 patients, we detected genetic allelic variants affecting TPMT activity; in 1 case, it was an unpublished heterozygous variant c.85T>C (p.W29R); of those, 15 patients were switched from AZA to a different medication, and 1 patient was prescribed a reduced dose of AZA. Our findings show the importance of testing for variants of the TPMT gene before the administration of AZA in clinical rheumatology practice. Patients with documented episodes of leukopenia or elevated liver biochemical tests while on AZA should undergo TPMT genotype testing and/or TPMT enzyme activity testing.