Myeloperoxidase deficiency
Encyclopedia
Myeloperoxidase deficiency is a common genetic disorder
featuring deficiency, either in quantity or function, of myeloperoxidase
, an enzyme found in certain phagocytic
immune cells, especially polymorphonuclear leukocytes.
It can appear similar to chronic granulomatous disease
on some screening tests.
infections), the majority of individuals with MPO
deficiency show no signs of immunodeficiency.
The lack of severe symptoms suggest that role of myeloperoxidase in the immune response must be redundant to other mechanisms of intracellular killing of phagocytosed bacteria.
Patients with MPO deficiency have a respiratory burst with a normal nitro blue tetrazolium
(NBT) test because they still have NADPH oxidase activity, but do not form bleach due to their lack of myeloperoxidase activity. This is in contrast to chronic granulomatous disease in which the NBT test is 'positive' due to the lack of NADPH oxidase activity (positive test result means neutrophils fail to turn blue).
Genetic disorder
A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....
featuring deficiency, either in quantity or function, of myeloperoxidase
Myeloperoxidase
Myeloperoxidase is a peroxidase enzyme that in humans is encoded by the MPO gene. Myeloperoxidase is most abundantly expressed in neutrophil granulocytes . It is a lysosomal protein stored in azurophilic granules of the neutrophil...
, an enzyme found in certain phagocytic
Phagocyte
Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek phagein, "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek kutos, "hollow vessel". They are...
immune cells, especially polymorphonuclear leukocytes.
It can appear similar to chronic granulomatous disease
Chronic granulomatous disease
Chronic granulomatous disease is a diverse group of hereditary diseases in which certain cells of the immune system have difficulty forming the reactive oxygen compounds used to kill certain ingested pathogens...
on some screening tests.
Presentation
Although MPO deficiency classically presents with immune deficiency (especially candida albicansCandida albicans
Candida albicans is a diploid fungus that grows both as yeast and filamentous cells and a causal agent of opportunistic oral and genital infections in humans. Systemic fungal infections including those by C...
infections), the majority of individuals with MPO
MPO
- Astronomy :* Mercury Planetary Orbiter, one component of the BepiColombo mission to Mercury* Minor Planet Circulars Orbit Supplement, an astronomical publication from the Minor Planet Center...
deficiency show no signs of immunodeficiency.
The lack of severe symptoms suggest that role of myeloperoxidase in the immune response must be redundant to other mechanisms of intracellular killing of phagocytosed bacteria.
Patients with MPO deficiency have a respiratory burst with a normal nitro blue tetrazolium
Nitro blue tetrazolium chloride
Nitro blue tetrazolium is a chemical compound composed of two tetrazole moieties. It is used in immunology for sensitive detection of alkaline phosphatase . NBT serves as the oxidant and BCIP is the AP-substrate ....
(NBT) test because they still have NADPH oxidase activity, but do not form bleach due to their lack of myeloperoxidase activity. This is in contrast to chronic granulomatous disease in which the NBT test is 'positive' due to the lack of NADPH oxidase activity (positive test result means neutrophils fail to turn blue).