CYP2C9 and Decreased total leukocyte count: Potential genetic loci that have so far been identified are two candidate loci on chromosome 9 (one of which located in the SVEP1 gene previously implicated in hematopoiesis),25 NAT2, CYP2C9, and CYP2C19 gene polymorphisms26 and the presence of HLA24.27 Further studies are needed to gain additional insights into genetic predisposition to and the mechanisms underlying metamizole-induced leukopenia.