6-MP was discontinued more often in patients with TPMT*3A and TPMT*3C alleles (14-fold) as a result of leucopenia, anemia, and/or thrombocytopenia (P = 0.004).
The study confirmed the association of thiopurine methyltransferase heterozygosity with leucopenia and neutropenia in ALL patients and reported a significant association between inosine triphosphatase IVS2+21A-->C variants with thrombocytopenia (P = 0.012).