Complement deficiency

Last updated: Wednesday, 24, November, 2010
Key InformationAppropriate Tests

Complement CH50 or CH100; complement components C3 and C4.

Further testing in specialised laboratory, consult pathologist.

Congenital (primary) deficiency

Complement CH50 or CH100 levels frequently reduced.
  • SLE-like syndromes
Complement components C1q and C2; complement components C3 and C4; complement component C4 allotype.
  • Recurrent infection
C3. C3 receptor.
  • Recurrent neisserial infection
C5, C6, C7 or C8 components.
  • Angioedema
  • Serum mannose binding lectin
  • Mannose binding lectin genotyping

Acquired deficiency

Complement CH50, CH100 levels frequently reduced.
C3 and C4 may be reduced.
  • Gram-negative (endotoxic) shock
C3 reduced, C4 normal; tests rarely indicated.
  • Serum sickness
C3 and C4 reduced.
  • Subacute bacterial endocarditis
See Endocarditis, infective		C3 and C4 may be reduced; tests rarely indicated.
  • Mesangiocapillary glomerulonephritis
See Glomerulonephritis (GN)		C3 reduced. C3 Nephritic factor.
  • Partial lipodystrophy
C3 reduced. C3 Nephritic factor.