Partial Myeloperoxidase Deficiency in a Case of Preleukaemia.

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Abstract
A patient with a refractory anaemia preceding acute myeloblastic leukaemia had an increased susceptibility to infection due to Staphylococcus aureus. 36% of neutrophils lacked myeloperoxidase (MPO) activity and, in vitro, these polymorphonuclear neutrophils (PMN) had a defect of bactericidal activity against Staphylococcus aureus. Cytochemical studies of phagocytosis with the electron miscroscope have shown that the degranulation of primary granules (MPO+ or MPO-) was normal after phagocytosis of Escherichia coli which were normally lysed. A defective destruction of Staphylococcus aureus and Candida albicans was observed in some PMN with or without MPO activity, suggesting that MPO deficiency itself was not the only cause of this defect. In PMN which appeared normal, most MPO(+) granules were unable to fuse with the phagocytic vacuole containing intact germs even after 90 min of contact. There was, therefore, in addition to a partial MPO deficiency, a defect in cellular degranulation. This defect, the mechanism of which is unknown, may be in part responsible for the defective bacterial degradation.