Primary “Hereditary”  MPO Deficiency Secondary “Acquired”  MPO Deficiency MPO Activity in neutrophils Absent (or low) in all cells Variable activity cell to cell (absentànormal) MPO Activity in Bone Marrow Absent Variable Concomitant diseases Sometimes Always Inherited Yes No

Table 1: Differentiation of primary and secondary MPO deficiency. Adapted from Lanza et al. [53].