Terminal complement pathway deficiency

Terminal complement pathway deficiency is a genetic condition affecting the complement membrane attack complex (MAC).

Terminal complement pathway deficiency
complement membrane attack complex

It involves deficiencies of C5, C6, C7, and C8. (While C9 is part of the MAC, and deficiencies have been identified,[1] it is not required for cell lysis.[2])

People with this condition are prone to meningococcal infection.[3] Vaccination may be recommended.[4]

Cause

Diagnosis

Suspect terminal complement pathway deficiency with patients who have more than one episode of Neisseria infection.

Complement tests
C4 (C) FB (A) C3 CH50 Conditions
 · ↓ ↓ ↓ PSG, C3 NeF AA
↓  · ↓  · HAE, C4D
 ·  ·  · ↓ TCPD
↓  · /↓ ↓ ↓ SLE
↑ ↑ ↑ ↑ inflammation

Initial complement tests often include C3 and C4, but not C5 through C9. Instead, the CH50 result may play a role in diagnosis: if the CH50 level is low but C3 and C4 are normal, then analysis of the individual terminal components may be warranted.

Treatment

Patients with terminal complement pathway deficiency should receive meningococcal and pneumococcal vaccinations. They can receive live vaccines.

References
  1. Lint TF, Zeitz HJ, Gewurz H (November 1980). "Inherited deficiency of the ninth component of complement in man". J. Immunol. 125 (5): 2252–7. PMID 7430628.
  2. Thomas M. Habermann; Mayo Clinic (1 November 2007). Mayo Clinic Internal Medicine Concise Textbook. CRC Press. pp. 30–. ISBN 978-1-4200-6749-1. Retrieved 14 November 2010.
  3. J.K. Sinha & S. Bhattacharya. A Text Book of Immunology. Academic Publishers. pp. 385–. ISBN 978-81-89781-09-5. Retrieved 14 November 2010.
  4. Frederick S. Southwick (10 December 2007). Infectious diseases: a clinical short course. McGraw Hill Professional. pp. 149–. ISBN 978-0-07-147722-2. Retrieved 14 November 2010.


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