Common variable immune deficiency (CVIDs) are the name for a group of conditions that affect how the body’s immune system makes antibodies and fights infections.
If you have a CVID you are unable to make protective antibodies and therefore become susceptible to infections. Both males and females can be affected by a CVID. The clinical features of a CVID can vary from mild in those who suffer only from infections, to severe in those with disease-related complications.
Antibodies belong to a particular type of protein called immunoglobulin, which is normally found in blood and body fluids. There are three major types of immunoglobulin, known as:
- Immunoglobulin G (IgG) – the most abundant and common immunoglobulin, found in blood and tissue fluids. IgG functions mainly against bacteria and some viruses.
- Immunoglobulin M (IgM) – found in the blood, IgM functions in much the same way as IgG but is formed earlier in the immune response.
- Immunoglobulin A (IgA) – found in blood, tears and saliva. IgA protects the tissues of the respiratory, reproductive, urinary and digestive systems.
All types are made up of antibodies against the germs that an individual has met during the course of his or her life.
People with a CVID have either low levels of immunoglobulin in their blood or none at all; all are unable to make functional antibodies of the IgG or IgA types, though some patients do make IgM antibodies. This means those affected can’t fight infection as well as people with a fully working immune system. Patients may have severe, persistent or repeated infections, often from the same germ. These infections are usually bacterial, but may also be viruses, parasites and fungi. The infections particularly affect the ears, sinuses, chest, lungs or gut – places that come into daily contact with infectious agents.
CVIDs are a range of different immune deficiencies, and the diagnosis is often used inappropriately to cover more severe ‘combined immunodeficiencies’ in which antibodies and immune T-cells do not work. The disorder is called ‘variable’ because of the extent and type of immune deficiencies. Furthermore, the clinical course varies from patient to patient. In some patients, there is a decrease in both IgG and IgA in the blood; in other patients, levels of all three major immunoglobulin types, IgG, IgA and IgM, may be decreased.
Since CVID patients are susceptible to bacterial infections due to missing antibodies, the aim of treatment is to replace those antibodies with purified immunoglobulins from the blood of healthy donors. Immunoglobulin therapy, combined with antibiotics for breakthrough infections, means that people with a CVID can live relatively normal lives with no restrictions on employment. Many patients with a CVID work in healthcare or on farms.
The immunoglobulin therapy aims to prevent both infections and thedevelopment of chronic lung disease. The outlook for patients with a CVID depends on how much damage has occurred to their lungs or other organs before diagnosis and how successfully infections can be prevented in the future by immunoglobulin therapy.