Therefore, after considering all other factors, our patient with the homozygous variants c.-3279T>G and A(TA)7TAA of UGT1A1 and unconjugated hyperbilirubinemia during ALL chemotherapy, without liver dysfunction, is unlikely to have hyperbilirubinemia attributable to chemotherapy adverse effects; rather, it is likely due to GS. Here, UGT1A1 is linked to acute lymphoblastic leukemia.