Safe 6-thioguanine therapy of a TPMT deficient Crohn's disease patient by using therapeutic drug monitoring

The immunosuppressive thiopurines, azathioprine (AZA) and 6-mercaptopurine (6-MP), have proven efficacy in steroid-dependant or refractory inflammatory bowel disease (IBD). In case of TPMT deficiency serious myelosuppression may occur. 6-thioguanine (6-TG), has been suggested in case of AZA and 6-MP resistant or intolerant patients. Our case demonstrates that very low dose 6-TG under close clinical surveillance and frequent therapeutic drug monitoring, may be a rescue drug for IBD-patients with low or without functional TPMT activity.