Traits

Traits linked to CIITA

class II major histocompatibility complex transactivator

The Human Phenotype Ontology links 67 traits to CIITA, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the immune system

Trait	How often it is seen
Reduced MHC II cell surface expression	Always
Recurrent respiratory infections	Very often (80–99%)
Abnormality of humoral immunity	Often (30–79%)
Recurrent bacterial infections	Often (30–79%)
Recurrent Candida infection	Often (30–79%)
Recurrent fungal infections	Often (30–79%)
Recurrent mucocutaneous candidiasis	Often (30–79%)
Recurrent protozoan infections	Often (30–79%)
Recurrent Staphylococcus aureus infection	Often (30–79%)
Recurrent viral infections	Often (30–79%)
Susceptibility to herpesvirus	Often (30–79%)
Autoimmunity	Sometimes (5–29%)
Skin rash	Sometimes (5–29%)
Anti-citrullinated protein antibody positivity	Not recorded
Brain inflammation	Not recorded
Chronic lymphocytic meningitis	Not recorded
Recurrent chest infections	Not recorded
Rheumatoid factor positive	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Recurrent infection of the gastrointestinal tract	Very often (80–99%)
Chronic hepatitis due to cryptosporidium infection	Often (30–79%)
Diarrhea	Often (30–79%)
Protracted diarrhea	Often (30–79%)
Sclerosing cholangitis	Often (30–79%)
Bile duct inflammation	Not recorded
Biliary tract abnormality	Not recorded
Colitis	Not recorded
Malabsorption	Not recorded
Villous atrophy	Not recorded
Viral hepatitis	Not recorded

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Decreased total CD4+ T cell proportion	Often (30–79%)
Abnormal CD4:CD8 ratio	Sometimes (5–29%)
Autoimmune hemolytic anemia	Sometimes (5–29%)
Autoimmune neutropenia	Sometimes (5–29%)
Autoimmune thrombocytopenia	Sometimes (5–29%)
Low blood cell count	Sometimes (5–29%)
Low blood neutrophil count	Sometimes (5–29%)
Low T cell count	Sometimes (5–29%)

Abnormal cellular phenotype

Trait	How often it is seen
Impaired T cell function	Very often (80–99%)
Decreased circulating antibody level	Often (30–79%)
Decreased mitogen-induced T-cell proliferation	Sometimes (5–29%)
Panhypogammaglobulinemia	Sometimes (5–29%)
Agammaglobulinemia	Not recorded
Cutaneous anergy	Not recorded

Laboratory abnormality

Trait	How often it is seen
Decreased circulating beta-2-microglobulin concentration	Often (30–79%)
Elevated circulating C-reactive protein concentration	Not recorded
Fever	Not recorded
High ESR	Not recorded
Joint swelling	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Nasal inflammation	Often (30–79%)
Sinus disease	Often (30–79%)
Abnormal facial shape	Rarely (1–4%)
Recurrent colds	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Joint stiffness	Not recorded
Polyarticular arthritis	Not recorded
Rheumatoid arthritis	Not recorded
Trigger finger	Not recorded

Abnormality of limbs

Trait	How often it is seen
Interphalangeal joint erosions	Not recorded
Swan neck-like deformities of the fingers	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Difficulty articulating speech	Rarely (1–4%)
Inability to coordinate movements when walking	Rarely (1–4%)

Constitutional symptom

Trait	How often it is seen
Fatigue	Not recorded
Joint pain	Not recorded

Growth abnormality

Trait	How often it is seen
Faltering weight	Often (30–79%)
Weight loss	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Inflammation of blood vessel	Not recorded

Abnormality of the ear

Trait	How often it is seen
Acute middle ear infection	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Frequent urinary tract infections	Not recorded

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to CIITA and how often each is seen. Find out more at hpo.jax.org.

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