When your body feels it is threatened or under attack, it makes special proteins called immunoglobulins, or antibodies. These antibodies are made by the plasma cells. They are released throughout the body to help kill bacteria, viruses, and other germs. The body makes three major types of immunoglobulins: immunoglobulin A, immunoglobulin G, and immunoglobulin M.
Immunoglobulin G, also known as IgG, is the most common type. It makes up as much as 80 percent of all the antibodies in the blood. IgG is broken into four different subclasses, IgG1 through IgG4. IgG is always available to help ward off infections. It's also ready to reproduce and attack when foreign substances enter the body.
When the body doesn't produce enough IgG, the condition is known as an IgG deficiency. People with IgG deficiency are more likely to get infections.
Infections that commonly affect people with IgG deficiency include:
Sinus infections and other respiratory infections
Infections that result in sore throat
Rarely, severe and life-threatening infections
In some people, the infections cause scarring that damages the airways and lung function. This can affect breathing. People with IgG deficiency also often find that pneumonia and influenza vaccines don't keep them from getting these infections.
Although it's not known what causes IgG deficiency, genetics may play a role. IgG deficiency is also thought to be related to another immunoglobulin deficiency, because it often occurs in people who are also deficient in immunoglobulin A (IgA deficiency) and immunoglobulin M (IgM deficiency).
A blood test that measures immunoglobulin can show abnormally low levels of the antibodies and diagnose IgG deficiency. It's possible to have a normal level of total IgG, so the testing of the IgG subclasses is important. Tests can also be done on saliva and cerebrospinal fluid, but testing your blood is the most common method.
Treatment depends on how severe your symptoms and infections are. When the symptoms develop later in life, the condition is harder to manage, and the person tends to have more infections.
If infections are not disrupting your daily life, treating them right away may be enough. If you get frequent or chronic severe infections, you may benefit from ongoing treatment to prevent illness or reduce symptoms or frequency. This may mean taking a daily antibiotic to ward off infections. It may be necessary to alternate between different antibiotics if infections and symptoms still occur.
Some people who suffer from severe infections may be resistant to antibiotic treatment. They may need an immunoglobulin replacement treatment (immunoglobulin therapy) to help boost the body's immune system rather than relying on antibiotics to prevent infections.