What are IgG deficiencies?

An IgG deficiency is a health problem in which your body doesn’t make enough immunoglobulin G (IgG). Normally, IgG is the most abundant antibody in the blood. It helps prevent infections. So, people with IgG deficiency are more likely to get infections.

When your body feels it is under attack, it makes special proteins called immunoglobulins, or antibodies. These antibodies are made by the plasma cells. They are let loose throughout the body to help kill bacteria, viruses, and other germs. There are several types and subtypes of immunoglobulins.

IgG is ready to multiply and attack when foreign substances get into the body. When you don't have enough IgG or they are not working properly, you are more likely to get infections.

What causes IgG deficiencies?

IgG deficiency may be primary or secondary. Researchers don't know what causes primary IgG deficiency, but genetics may play a role. Secondary IgG deficiency may be caused by:

• Aging

• Malnutrition

• Chemotherapy medicines and long-term corticosteroids

• Infections such as HIV

What are the symptoms of an IgG deficiency?

Infections that most often affect people with IgG deficiency are:

• Sinus infections and other respiratory infections

• Digestive tract infections

• Ear infections

• Pneumonia

• Bronchitis that keeps coming back. It can lead to permanent lung damage.

• Infections that cause a sore throat

• Severe and life-threatening infections (rare)

In some people, infections cause scarring that harms the airways and how the lungs work. This can affect breathing. People with IgG deficiency also often find that pneumonia and the flu vaccines don’t keep them from getting these infections.

How is an IgG deficiency diagnosed?

Your healthcare provider will order a blood test that measures immunoglobulin levels to diagnose IgG deficiency. It’s possible to have a normal level of total IgG, so it's important that your provider test the IgG subclasses. Tests can also be done on saliva and cerebrospinal fluid. But a blood test is the most common. In some cases, your healthcare provider (usually an immunologist) will see how your immune system responds after getting a vaccine.

How is an IgG deficiency treated?

Treatment depends on how bad your symptoms and infections are. When the symptoms come on later in life, the health problem is harder to manage. You may also have more infections.

If infections are not getting in the way of your daily life, treating them right away may be enough. If you get frequent or severe infections that keep coming back, you may need ongoing treatment such as a daily antibiotic. This will help to prevent sickness or reduce symptoms or how often they happen. You may need to switch between other antibiotics if infections and symptoms still happen.

Some people who have severe infections don't respond well enough to antibiotic treatment. They may need immunoglobulin therapy to help boost their immune system rather than relying on antibiotics to prevent infections. This therapy contains pooled IgG antibodies from healthy donors with normal immune systems. If you need this, you may get the medicine through an IV (intravenous) or as a shot. In some cases you can give yourself a shot at home.

When should I call my healthcare provider?

If you have been diagnosed with IgG deficiency, call your healthcare provider whenever you have signs of infection. This is true even if you just have a cold. 

Key points

• Immunoglobulin G (IgG) is normally the most abundant antibody in the blood.

• People with IgG deficiency are more likely to get infections.

• Although researchers don't know what causes primary IgG deficiency, genetics may play a role.

• When the symptoms come on later in life, the health problem is harder to manage, and you may have more infections.

• Treatment depends on how bad your symptoms and infections are. It can range from treating infections early to taking preventive antibiotics to getting infusions or shots of immunoglobulin replacement therapy.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.