{"6-mercaptopurine can be affected by a patient's TPMT and NUDT15 phenotype. This patient is predicted to be a NUDT15 poor metabolizer and is at high risk for life threatening myelosuppression with normal doses of 6-mercaptopurine and should receive drastically reduced doses. For malignancy, reduce daily dose by 10-fold (~90% dose reduction) and reduce frequency to 3 times per week instead of daily (e.g., 10 mg/m2/day given just 3 days/week). During therapy, adjust 6-mercaptopurine doses based on degree of myelosuppression and disease-specific guidelines. It usually takes at least 4-6 weeks of stable dosing to reach steady state after each dose adjustment. If myelosuppression occurs, emphasis should be on reducing 6-mercaptopurine over other agents. For non-malignancy, consider alternative non-thiopurine immunosuppressant therapy. TPMT phenotype could not be assigned based on genotyping performed. Consider evaluating TPMT erythrocyte activity to assess TPMT phenotype. Erythrocyte TPMT activity test results can be falsely low at diagnosis of leukemia and is unreliable in the case of recent red blood cell transfusions. If 6-mercaptopurine is required and TPMT status is unknown, monitor closely for toxicity. Please consult a clinical pharmacist for more information."}