B acute lymphoblastic leukemia patients were observed to be at a greater risk of bacterial infections and present prolonged episodes of febrile neutropenia if they possessed a medium-/high-risk haplotype for FCN2 of GGATG, GGACG, or AGACG (all haplotypes composed of -986/-602/-4/+6359/+6424) [101]. The gene discussed is FCN2; the disease is bacterial infectious disease.