Based on NUDT15 status, for non-malignant conditions, consider alternative non-thiopurine immunosuppressant therapy. For malignant conditions, start with drastically reduced normal daily doses (reduce daily dose by 10-fold) and adjust doses of azathioprine based on degree of myelosuppression and disease-specific guidelines. Allow 4-6 weeks to reach steady-state after each dose adjustment (PMID 16530578, 11302950, 15606506, 16530532, 12477776). TPMT phenotype could not be assigned based on genotyping performed. Consider evaluating erythrocyte TPMT activity to assess TPMT phenotype. If thiopurines are required and TPMT status is unknown, monitor closely for toxicity.