C4A deficiency

C4 is encoded by two genes C4A and C4B and is evolutionarily related to C3, C5, and alfa2 macroglobulin. The two isotypes are encoded by two distinct loci within the major histocompatibility complex (MHC) class III region on chromosome 6. Both genes are higly polymorphic.

Alternative names

Complement component 4A deficiency


  • Defects of the classical complement cascade proteins
    • C4 deficiency


Autosomal recessive


+120810 Complement component 4A; C4A

Cross references

Phenotypically related immunodeficiencies

IDR factfile for C4B deficiency


Incidence is not known.