ABSTRACT
Myeloperoxidase (MPO), an iron-containing heme protein localized in the azurophilic granules of neutrophils and in the lysosomes of monocytes, is involved in the killing of several micro-organisms and foreign cells, including bacteria, fungi, viruses, red cells, and malignant or nonmalignant nucleated cells. We experienced a case of myeloperoxidase deficiency in a 10-month-old male patient with recurrent skin abscess. His leukocyte count was 12,340/microliter with 35% neutrophils. Compared with normal control neutrophils, the patient's neutrophils in the peripheral blood showed normal chemotaxis and phagocytic activity, increased respiratory burst activity in the stimulation with PMA, but, revealed the decreased microbial killing activity. These findings were suggestive of neutrophil granular defects such as myeloperoxidase deficiency and other specific granule content deficiency. The patient's neutrophils showed partially decreased MPO activity in the MPO stain.