There is a strong association of the FLT3 738T genotype with leucopenia; FLT3 738T, ABCB1 1236T, ABCB1 3435T, ABCB1 2677T, ABCG2 421A alleles and the ABCB1-3435-1236-2677 TTT haplotype with neutropenia; and primary resistance and inferior survival with the ABCB1-3435-1236-2677 TTT haplotype [152]. This evidence concerns the gene FLT3 and Decreased total neutrophil count.