Terminal complement pathway deficiency
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| Terminal complement pathway deficiency | |
|---|---|
 | |
| complement membrane attack complex |
Terminal complement pathway deficiency is a genetic condition affecting the complement membrane attack complex (MAC).
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]
Suspect terminal complement pathway deficiency in patients with more than one Neisseria infection episode.
| 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.