Five (8.6%) of 58 children with ALL had a polymorphic TPMT allele: 4 (3.4%) were heterozygous for TPMT*3A (G460A and A719G), and one (0.9%) was heterozygous for TPMT*3C (A719G).
A patient, exhibiting neutropenia on 6-MP was observed to be G460A-homozygote, while, two Acute Lymphoblastic Leukemia (ALL) patients with side-effects exhibited wild-type alleles.