Schematic representation of MPO genotypes in the normal population and in AML subtypes. (A) Relative percentage of SpSp, SpN, and NN genotypes in 111 normal donors. (B) Relative number of SpSp, SpN heterozygotes, or NN homozygotes in the various AML subtypes. Cases are from Table 1. Subtypes M0 through M6 approximate early to late stages of myeloid differentiation. The highest proportions of the SpSp genotype are seen in APL-M3 and -M4 subtypes, which have high MPO expression.