Microscopic polyangiitis
Encyclopedia
Microscopic polyangiitis (also known as "Microscopic polyarteritis," "Microscopic polyarteritis nodosa," "MPA") is an ill-defined autoimmune disease
characterized by pauci-immune, necrotizing, small-vessel vasculitis
without clinical or pathological evidence of necrotizing granulomatous inflammation
.
Purpura
and livedo
may be present.
(a constituent of neutrophil granules), and protein
and red blood cells in the urine
.
The test for anti-glomerular basement membrane antibody
(GBM), which is positive in Goodpasture's syndrome
, is negative.
. These antibodies will circulate at low levels until a pro-inflammatory trigger - such as infection, malignancy, or drug therapy. The trigger upregulates production of p-ANCA. Then, the large number of antibodies make it more likely that they will bind a neutrophil. Once bound, the neutrophil degranulates. The degranulation releases toxins that cause endothelial injury, that is, damage to vessels of glomeruli.
, alternated or combined with cytotoxic drugs, such as cyclophosphamide
or azathioprine
.
Plasmapheresis
may also be indicated in the acute setting to remove ANCA antibodies.
Rituximab
has been investigated, and in April 2011 approved by the FDA
when used in combination with glucocorticoid
s.
Autoimmune disease
Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body actually attacks its own cells. The immune system mistakes some part of the body as a pathogen and attacks it. This may be restricted to...
characterized by pauci-immune, necrotizing, small-vessel vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
without clinical or pathological evidence of necrotizing granulomatous inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
.
Presentation
Because many different organ systems may be involved, a wide range of symptoms is possible in MPA.Purpura
Purpura
Purpura is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin...
and livedo
Livedo
Livedo refers to a form of skin discoloration.* Livedo reticularis* Livedoid dermatitis* Livedoid vasculitis...
may be present.
Diagnosis
Laboratory tests show an increased sedimentation rate, reduced red blood count, perinuclear antineutrophil cytoplasmic antibodies (p-ANCA) directed against myeloperoxidaseMyeloperoxidase
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...
(a constituent of neutrophil granules), and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
and red blood cells in the urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
.
The test for anti-glomerular basement membrane antibody
Anti-glomerular basement membrane antibody
Anti-glomerular basement membrane antibody is an antibody which is found in Goodpasture's syndrome but not found in microscopic polyangiitis....
(GBM), which is positive in Goodpasture's syndrome
Goodpasture's syndrome
Goodpasture’s syndrome is a rare disease characterized by glomerulonephritis and hemorrhaging of the lungs...
, is negative.
Cause
This condition, the clinical picture of which may include many features of systemic lupus erythematosis, has been reported. While the mechanism of disease has yet to be fully elucidated, the leading hypothesis is that the process is begun with an autoimmune process of unknown etiology that triggers production of p-ANCAANCA
ANCA Pty Ltd is an Australia company which designs and manufactures CNC grinding machines. The company was founded in 1974 by Pat Boland and Pat McCluskey in Melbourne, Australia....
. These antibodies will circulate at low levels until a pro-inflammatory trigger - such as infection, malignancy, or drug therapy. The trigger upregulates production of p-ANCA. Then, the large number of antibodies make it more likely that they will bind a neutrophil. Once bound, the neutrophil degranulates. The degranulation releases toxins that cause endothelial injury, that is, damage to vessels of glomeruli.
Treatment
The customary treatment involves long term dosage of prednisonePrednisone
Prednisone is a synthetic corticosteroid drug that is particularly effective as an immunosuppressant drug. It is used to treat certain inflammatory diseases and some types of cancer, but has significant adverse effects...
, alternated or combined with cytotoxic drugs, such as cyclophosphamide
Cyclophosphamide
Cyclophosphamide , also known as cytophosphane, is a nitrogen mustard alkylating agent, from the oxazophorines group....
or azathioprine
Azathioprine
Azathioprine is a purine analogue immunosuppressive drug. It is used to prevent organ rejection following organ transplantation and to treat a vast array of autoimmune diseases, including rheumatoid arthritis, pemphigus, inflammatory bowel disease , multiple sclerosis, autoimmune hepatitis, atopic...
.
Plasmapheresis
Plasmapheresis
Plasmapheresis is the removal, treatment, and return of blood plasma from blood circulation. It is thus an extracorporeal therapy...
may also be indicated in the acute setting to remove ANCA antibodies.
Rituximab
Rituximab
Rituximab, sold under the trade names Rituxan and MabThera, is a chimeric monoclonal antibody against the protein CD20, which is primarily found on the surface of B cells...
has been investigated, and in April 2011 approved by the FDA
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
when used in combination with glucocorticoid
Glucocorticoid
Glucocorticoids are a class of steroid hormones that bind to the glucocorticoid receptor , which is present in almost every vertebrate animal cell...
s.
See also
- ANCA-associated vasculitidesANCA-associated vasculitidesANCA-associated vasculitides are diseases caused by vasculitis in which antineutrophil cytoplasmic antibodies can be detected in the blood.-Types:Three main AAVs are Churg-Strauss syndrome, microscopic polyangiitis and Wegener's granulomatosis...
- Polyarteritis nodosaPolyarteritis nodosaPolyarteritis nodosa is a vasculitis of medium & small-sized arteries, which become swollen and damaged from attack by rogue immune cells. Polyarteritis nodosa is also called Kussmaul disease or Kussmaul-Maier disease...
- List of cutaneous conditions
External links
- Overview at Johns HopkinsJohns HopkinsJohns Hopkins was a wealthy American entrepreneur, philanthropist and abolitionist of 19th-century Baltimore, Maryland, now most noted for his philanthropic creation of the institutions that bear his name, namely the Johns Hopkins Hospital, and the Johns Hopkins University and its associated...
- Overview at Cleveland ClinicCleveland ClinicThe Cleveland Clinic is a multispecialty academic medical center located in Cleveland, Ohio, United States. The Cleveland Clinic is currently regarded as one of the top 4 hospitals in the United States as rated by U.S. News & World Report...