STUDY: Why is acute leukemia more common in males? A possible sex-determined risk linked to the ABO blood group genes.

JOURNAL: Ann Hematol 1999 May;78(5):233-6

AUTHORS: Jackson N, Menon BS, Zarina W, Zawawi N, Naing NN.

ABSTRACT: Acute leukemia is more common in males at almost every age, and this fact remains unexplained. A study was carried out in northeast peninsular Malaysia, where the population is predominantly Malay, to examine whether there was a difference in ABO blood group distribution between males and females with acute leukemia (AL). The ABO blood groups of 109 male and 79 female patients with AL (98 ALL, 90 AML) were compared with those of 1019 controls. In the control population, 39.7% were group O. Among males with AL, 39.4% were group O, whereas among females with AL, the proportion was 24.1% (p=0.03). The same trend to a lower proportion of group O among females was seen when the group was divided into adult/pediatric or lymphoblastic/myeloblastic groups, though these differences were not statistically significant. If these findings can be confirmed, they suggest the presence of a "sex-responsive" gene near to the ABO gene locus on chromosome 9, which relatively protects group O women against AL, at least in our population. The existence of such a gene might also partly explain why acute leukemia, and possibly other childhood cancers, are more common in males.

COMMENTARY: Here we again see the manifestation of ABO blood type in a much wider context than the simple manifestation of an antigen on a red blood cell (which, unfortunately, is all that they teach you in medical school). Gene linkage (the tendency of clusters of genes to transfer together) may help explain this phenomenon, since the O allele and the putative "protective sex responsive gene" probably only transfer together on the condition of the outcome of sex-determination (female).