Regulatory factor X-associated protein deficiency

Defects in RFXAP are a cause of hereditary MHC class II deficiency, also known as Bare Lymphocyte Syndrome (BLS) or HLA class II-deficient combined immunodeficiency). RFXAP is linked with BLS complementation group D. The disease is very rare; only approximately 70 patients from 57 unrelated families have been reported worldwide.

Alternative names

RFXAP deficiency

Bare Lymphocyte Syndrome type 2 (BLS)

RFXAP (complementation group D)


  • Combined B and T cell immunodeficiencies
    • Major histocompatibility complex class II deficiency


Autosomal recessive


#209920 Bare lymphocyte syndrome, type II

*601861 Regulatory factor X-associated protein; RFXAP


Incidence is not known yet.