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Updated on May 15, 2025
Immunoglobulin replacement therapy is the main treatment for primary immunodeficiency (PI).
PI is a group of hundreds of rare genetic disorders that interfere with the normal functioning of the immune system and cause a person to be more vulnerable to infections, such as respiratory infections, ear infections, and skin infections.
A person with PI will be more likely to have infections that are severe, difficult to treat, or have uncommon causes. Complications from PI can include organ damage, autoimmune disorders, delayed growth, and cancer.
Immunoglobulin replacement therapy
Immunoglobulins (Ig) are proteins that help the body fight infections. They are also called antibodies. Immunoglobulin infusions contain high concentrations of these proteins collected from donated human plasma.
Receiving these infusions regularly helps strengthen the immune system, increasing its ability to fight off viruses, infectious bacteria, fungal infections, and other disease-causing pathogens.
Immunoglobulin infusions do not cure PI and must be administered regularly, usually every 1 to 4 weeks. The infusion schedule will depend on the person being treated and the type of immunoglobulin being used.
How can Ig infusions be administered?
Immunoglobulin infusions can be given in two ways, intravenously or subcutaneously. Intravenous immunoglobulin (IVIg) is delivered into a vein and directly into the bloodstream. Subcutaneous immunoglobulin (SCIg) is delivered into the layer of tissue just below the skin, called the subcutaneous tissue. These infusions are usually administered in the thigh, lower abdomen, or outer buttocks.
Are there potential advantages with SCIg?
While both IVIg and SCIg are effective treatment options, SCIg can offer a few potential advantages.
Self-administration
One of the most frequently cited advantages that SCIg offers is that these infusions can be self-administered or administered with the help of a caregiver. This means that SCIg can be administered at home. Intravenous infusions must be administered by a healthcare provider and are typically administered in a healthcare office. A healthcare provider will provide training on how to administer a SCIg infusion.
Lower risk of systemic side effects
Like any medication, immunoglobulin replacement therapy can cause side effects, including systemic side effects like fever, chills, headache, nausea, muscle aches, joint pain, redness, swelling and itching. Systemic side effects occur less often and are typically less severe with SCIg compared to IVIg. As a result, SCIg does not usually require medication to manage side effects that IVIg sometimes requires.
However, systemic side effects can occur with either, and it should also be mentioned that most side effects from IVIg are mild.
Stable Ig levels
Also called the hypodermis, the subcutaneous layer is a layer of fatty tissue located just under the skin. Medicines that are injected or infused into the subcutaneous layer move through the body more slowly than medicines injected directly into the bloodstream. For a person with PI, SCIg can offer more steady levels of immunoglobulin over a longer period of time. However, this is not always an advantage—IVIg would be a better choice if immunoglobulin levels needed to be raised quickly.
Different treatments work for different people
Many people prefer SCIg infusions. However, many people prefer IVIg, and IVIg has its own advantages, such as less-frequent infusions, fewer needle sticks, and having every infusion administered by a healthcare professional. SCIg also requires a person to have the required dexterity, skill, and comfort in handling infusion equipment, while again, IVIg would be administered by a healthcare provider.
There is no one size fits all approach—different treatments will work better for different people. It’s worth taking some time to think about your current treatment and learn about what other treatment options are available. A healthcare provider will be your best source of information about treatment options and what is recommended based on your diagnosis and needs.
