C4B deficiency

C4 is encoded by two genes C4A and C4B and is 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, and to date, 35 different alleles have been described.

Alternative names

Complement component 4B deficiency


  • Defects of the classical complement cascade proteins
    • C4 deficiency


Autosomal recessive


*120820 Complement component 4b; C4B

Cross references

Phenotypically related immunodeficiencies

IDR factfile for C4A deficiency


Incidence is not known.