C4 binding protein α deficiency

Complement C4b-binding protein (C4BP) is a plasma protein synthesized in the liver and plays a regulatory role in the host defense complement system. C4BP binds to C4b and accelerates the decay of C4b2a. It is a cofactor for factor I inactivation of C4b. Mutations in C4BPA are associated with angioedema, cutaneous vasculitis, and arthritis.

Alternative names

Complement component 4-binding protein deficiency


  • Defects of complement regulatory proteins
    • C4-binding protein deficiency


Autosomal recessive


*120830 Complement component 4-binding protein, alpha; C4BPA

Cross references

Phenotypically related immunodeficiencies

IDR factfile for C4 binding protein β deficiency


Incidence is not known.