Myeloperoxidase-deficient polymorphonuclear leucocytes. (V): Relation to FAB-classification and neutrophil alkaline phosphatase activity in primary myelodysplastic syndromes.

In 45 cases of primary myelodysplastic syndrome; 16 refractory anaemia (RA), 11 RA with ring sideroblasts (RA+), 13 RA with excess of blasts (RAEB), 5 chronic myelomonocytic leukaemia (CMML), the relations between myeloperoxidase (MPO) activity in polymorphonuclear leucocytes (PMN), neutrophil alkaline phosphatase (NAP) activity, absolute number of PMN and thrombocytopenia were investigated. 11 patients (26%) showed abnormal numbers (greater than 4%) of MPO-deficient PMN and 27 (75%) showed abnormal NAP activity (NAP score; greater than 134.0, less than 15.0), mostly decreased. No significant correlations between MPO activity and NAP activity were demonstrated, nor were any significant correlations found with the other parameters investigated. The FAB-subtypes, RAEB and CMML, showed a significant correlation to thrombocytopenia (p = 0.028) and to pancytopenia (p = 0.024). The findings may support the view that at least some of the myelodysplastic syndromes may be fundamentally the same disease as acute myeloid leukaemia.