RESUMO
Associating the risk of childhood acute lymphoblastic leukemia (ALL) with genetic predisposition is still a challenge. Here, we discuss two non-twinned sibs (girl and boy) diagnosed with B-cell precursor (BCP-ALL) and ETV6-RUNX1. BCP-ALL clinical onset occurred 10months apart from each diagnosis. One child is alive in complete continuous remission, whereas, the other relapsed and evolved to death with resistance to ALL treatment. Despite the fact that BCP-ALL with ETV6-RUNX1 usually results in a very good prognosis, the sibs experienced divergent outcomes; a remarkable difference in one child that presented a more aggressive disease was higher leukocytosis associated with IKZF1 deletion. The familial history of cancer and genetic susceptibility was explored. The sibs were absolutely identical in all 17 loci of genes tested; GSTM1, GSTT1, NQO1, TP53, and TP63 were wild-type, whereas at least one copy of the variant allele for IKZF1, ARID5B, PTPRJ and CEBPE was present. The familial pattern of ETV6 was tested by the 12p microsatellite analysis and demonstrated that deletions occurred in one child but not the other, while heterozygous patterns were found in the parents. Altogether, our data suggest that genetic predisposition aligned with chance haa an additive effect in BCP-ALL outcome.