Complement deficiency

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Complement deficiency
Classification and external resources
ICD-10 D84.1
ICD-9 279.8
OMIM 217000 120820, 120900, 610102
DiseasesDB 1847 1869, 1873, 7384, 34381
eMedicine med/419 ped/447

Complement deficiency is an immunodeficiency of absent or suboptimal functioning of one of the complement system proteins.[1]

The disorders can be divided into two categories:

  • Disorders of the proteins that act to activate the complement system (such as C3) can lead to an underactive response, causing greater susceptibility to infections.

Because there are redundancies in the immune system, many complement disorders are never diagnosed. A recent study estimated that less than 10% are identified.[2]


Hypocomplementemia may be used more generally to refer to decreased complement levels[3] while secondary complement disorder is to low complement levels that are not directly due to a genetic cause but secondary to another medical condition.[4]

The total hemolytic complement complement CH50 level in the blood will be low or undetectable with complement deficiencies.

Individual complement levels can be used to distinguish conditions:

Vaccinations for encapsulated organisms is crucial for preventing infections in complement deficiencies.


C2 deficiency is prevalent in 120,000 people in Western countries.[7] It occurs in about 1 in 10,000 persons.[8]

See also[edit]


  1. ^ Sherwood L. Gorbach; John G. Bartlett; Neil R. Blacklow (2004). Infectious diseases. Lippincott Williams & Wilkins. pp. 11–. ISBN 978-0-7817-3371-7. Retrieved 30 May 2010. 
  2. ^ Sjöholm AG, Jönsson G, Braconier JH, Sturfelt G, Truedsson L (2006). "Complement deficiency and disease: an update". Mol. Immunol. 43 (1–2): 78–85. doi:10.1016/j.molimm.2005.06.025. PMID 16026838. 
  3. ^ "hypocomplementemia" at Dorland's Medical Dictionary
  4. ^
  5. ^ Harrison's Principles of Internal Medicine, 17th edition
  6. ^ Bruce L. Zuraw, M.D. (September 4, 2008). "Hereditary Angioedema". N Engl J Med 2008 359: 1027–1036. doi:10.1056/NEJMcp0803977. PMID 18768946. 
  7. ^
  8. ^