Common variable immunodeficiency

Common variable immunodeficiency (CVID) is a group of 20-30 primary immunodeficiencies (PIDs) which have a common set of symptoms but with different underlying causes. more...

Causes and types

CVID's underlying causes are different, but the result of these are that the patient doesn't produce sufficient antibodies in response to exposure to pathogens. As a result, the patient's immune system fails to protect them against common bacterial and viral (and occasionally parasitic and protozoal) infections. The net result is that the patient is prone to illness. Both parts of the immune system (the cellular and humoral system) are affected, hence its classification as a combined immunodeficiency.

Because CVID is a catch-all diagnosis, which encompasses a number of as-yet undifferentiated disorders, the cause of each specific disorder is different so one can't identify a single common theme. Some cases appear to be genetic, similarly to severe combined immunodeficiency (SCID), some appear to be environmental in some way, some may be pathogenic (with Epstein-Barr virus implicated by some informal research). Most of the diagnoses are probably a combination of genetic predisposition along with a pathogenic or envirogenic trigger.

Symptomology

Symptoms of CVID are:

• hypogammglobulinaemia, or low levels of immunoglobulin G (IgG)
• many patients have low levels of immunoglobulin A (IgA) and immunoglobulin M (IgM)
• polyarthritis, or joint pain, spread across most joints, but specifically fingers, wrists, elbows, toes, ankles and knees
• repeated incidence of infections which respond to antibiotics or antivirals, specifically: upper respiratory tract infections (URTIs), sinusitis, tonsilitis, epiglottitis, dermatological abcesses/boils (often, but not exclusively, facial and axillary), pneumonia, bronchitis, pleurisy, stomach/intestinal infections, colds, influenza, shingles, conjunctivitis
• diarrhoea (often arises as a result of "minor" intestinal infections, including protozoal and parasitic infections)
• bronchiectasis (lung tissue damage as a result of repeated chest infections) leading to shortness of breath
• poor titer levels in response to vaccination. Responsiveness may be tested after administration of polysaccharide and non-polysaccharide coated pathogens (e.g. streptococci and tetanus respectively)
• children may show a "failure to thrive" - they may be underweight and underdeveloped compared with "normal" peers
• patients may lose weight

Diagnosis normally takes in excess of two years, and diagnosis is often made in the second or third decade of life after referral to an immunologist.

As with several other immune cell disorders, CVID can predispose for some skin cancers and lymphoma. There also appears to be a predilection for autoimmune diseases. However, these appear to be relatively rare, with a risk of about 7%.

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