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Detailed information of MYELOPEROXIDASE DEFICIENCY
MYELOPEROXIDASE DEFICIENCY
DEFINITION:
A disorder of neutrophil function characterized by dysfunctional
azurophil granules resulting in mild or no clinical features.
EPIDEMIOLOGY:
- incidence: ½,000
- age of onset:
- risk factors:
- familial - autosomal recessive
- chrom.#: 17q21.3-q22
- gene: ?
PATHOGENESIS:
- neutrophils contain two distinct sets of granules:
azurophils and specific
- peroxidase positive
- form only during myeloblast and promyelocyte
differentiation
- contain unique bactericidal proteins
- peroxidase, defensins, lysozyme
- contain unique acid hydrolases and neutral proteinases
- contain myeloperoxidase (MPO) which is essential for the
chlorination and iodination of microbes ingested by
neutrophils
2. Genetic Defect
- genetic defect -> pretranslational defect -> diminished
amounts of MPO mRNA -> dysfunctional MPO protein in neutrophils
and monocyte azurophilic granules -> partial compromise of
bacteri-cidal activity (in vitro) -> in vivo deficiency can be
compen-sated for by non-oxidative bactericidal mechanisms -> no
or only mild clinical features
CLINICAL FEATURES:
- majority of patients are asymptomatic
- recurrent candidal infections in those with:
- diabetes mellitus
- other immunosuppressive disorders
INVESTIGATIONS:
- 2,000-15,000 WBC's (50-70% PMN's)
2. Neutrophil Function
- chemotaxis - normal
- superoxide release - increased
- bacterial killing
- mildly decreased
- minor defects in killing of S. aureus
- impaired killing of C. albicans
3. Cytochemistry (Wright Stain)
- lack of peroxidase activity
- normal alkaline phosphatase
MANAGEMENT:
- acute management of fungal infections
- genetic counselling
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Pediatric Database - MYELOPEROXIDASE DEFICIENCY
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