Microscopic polyangiitis
Other namesMicropolyangiitis, Wohlwill's disease
SpecialtyImmunology, rheumatology Edit this on Wikidata

Microscopic polyangiitis is an autoimmune disease characterized by a systemic, pauci-immune, necrotizing, small-vessel vasculitis without clinical or pathological evidence of granulomatous inflammation.

Signs and symptoms

Clinical features may include constitutional symptoms like fever, arthralgia, myalgia, loss of appetite, weight loss and fatigue. A variety of organs can be affected, which causes a wide range of symtoms such as cough, shortness of breath, hemoptysis (coughing up of blood), symtoms of kidney failure, skin manifestations (palpable purpura and livedo racemosa[1]), seizures or peripheral neuropathy, abdominal pain [2]

The kidneys are affected in up to 80% of cases with signs of blood and protein in the urine and the injury can lead to either rapidly or slowly progressive kidney failure. The lungs are affected in 20-50% of cases with findings of pulmonary hemorrhage, or chronic pulmonary fibrosis leading to respiratory failure.[3]

Causes

While the mechanism of the disease has yet to be fully elucidated, the leading hypothesis is that AAV (ANCA Associated Vasculitis) develops in patients with a genetic predisposition when an unknown cause triggers the production of p-ANCA. These antibodies will circulate at low levels until an environmental trigger—such as infection, malignancy, or drug therapy, causes the upregulation of neutrophils. The neutrophils bind to p-ANCAs and subsequently release inflammatory cytokines, reactive oxygen species and lytic enzymes that cause endothelial injury resulting to inflammation and necrosis of the small vessels.[4] The damage that is caused in the kidneys is specifically called necrotizing and crescentic glomerulonephritis.[5]

Diagnosis

Laboratory tests may reveal an increased sedimentation rate, elevated CRP and anemia. Kidney impairment will result to elevated creatinine in the blood and the detection of protein and red blood cells in the urine.

An important diagnostic test is the presence of perinuclear antineutrophil cytoplasmic antibodies (p-ANCA) with myeloperoxidase specificity[6] (a constituent of neutrophil granules)

Depending on which organ is affected special tests can be performed, such as renal biopsy in patients with kidney failure or electromyography in patients with peripheral neuropathy [7]

Differential diagnosis

The signs and symptoms of microscopic polyangiitis may resemble those of granulomatosis with polyangiitis (GPA) (another form of small-vessel vasculitis) but typically lacks the significant upper respiratory tract involvement (e.g., sinusitis) frequently seen in people affected by GPA.

Treatment

Immunsuppressive treatment is the gold standard management in order to achieve remission of the blood vessel inflammation that occurs in active microscopic polyangitis. The current immunosuppressive protocols consists of a combination of high dose of glucocorticoids in combination with either cyclophosphamide or Rituximab.[8] In cases of life threatening disease treatment with plasmapheresis can also be applied.

The immunosuppressive treatment is slowly tapered down under a period of several months but there is at the moment no consensus about the total duration of the therapy. Discontinuation of immunosuppression can be related to increased risk for disease flares.

See also

References

  1. ↑ Nagai Y, Hasegawa M, Igarashi N, Tanaka S, Yamanaka M, Ishikawa O (December 2008). "Cutaneous manifestations and histological features of microscopic polyangiitis". Eur J Dermatol. 19 (1): 57–60. doi:10.1684/ejd.2008.0566. PMID 19059827.
  2. ↑ Chung, Sharon A.; Seo, Philip (August 2010). "Microscopic Polyangiitis". Rheumatic Disease Clinics of North America. 36 (3): 545–558. doi:10.1016/j.rdc.2010.04.003. ISSN 0889-857X. PMC 2917831. PMID 20688249.
  3. ↑ Karras, Alexandre (August 2018). "Microscopic Polyangiitis: New Insights into Pathogenesis, Clinical Features and Therapy". Seminars in Respiratory and Critical Care Medicine. 39 (4): 459–464. doi:10.1055/s-0038-1673387. ISSN 1069-3424. PMID 30404112. S2CID 53207328.
  4. ↑ Nakazawa, Daigo; Masuda, Sakiko; Tomaru, Utano; Ishizu, Akihiro (February 2019). "Pathogenesis and therapeutic interventions for ANCA-associated vasculitis". Nature Reviews Rheumatology. 15 (2): 91–101. doi:10.1038/s41584-018-0145-y. hdl:2115/74654. ISSN 1759-4804. PMID 30542206. S2CID 54474335.
  5. ↑ Falk RJ, Jennette JC (July 2002). "ANCA are pathogenic—oh yes they are!". J. Am. Soc. Nephrol. 13 (7): 1977–9. doi:10.1681/ASN.V1371977. PMID 12089397.
  6. ↑ Seishima M, Oyama Z, Oda M (2004). "Skin eruptions associated with microscopic polyangiitis". Eur J Dermatol. 14 (4): 255–8. PMID 15319159.
  7. ↑ Houben, Eline; Bax, Willem A.; van Dam, Bastiaan; Slieker, Walentina A.T.; Verhave, Gideon; Frerichs, Fenneke C.P.; van Eijk, Izhar C.; Boersma, Wim G.; de Kuyper, Guido T.M.; Penne, Erik L. (October 2016). "Diagnosing ANCA-associated vasculitis in ANCA positive patients: A retrospective analysis on the role of clinical symptoms and the ANCA titre". Medicine. 95 (40): e5096. doi:10.1097/MD.0000000000005096. ISSN 0025-7974. PMC 5059091. PMID 27749588.
  8. ↑ Geetha, Duvuru; Jefferson, J. Ashley (2020-01-01). "ANCA-Associated Vasculitis: Core Curriculum 2020". American Journal of Kidney Diseases. 75 (1): 124–137. doi:10.1053/j.ajkd.2019.04.031. ISSN 0272-6386. PMID 31358311. S2CID 198983998.
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