Some Types of PI:

X-Linked Agammaglobulinemia (XLA)

X-linked agammaglobulinemia (XLA) is an inherited type of primary immunodeficiency (PI). People with XLA have a mutation in the gene that’s needed for the development of B lymphocytes, the immune cells that produce antibodies (immunoglobulins, or Ig). This results in a severe deficiency in antibodies – which are an important part of the body’s immune system and provide defense against infections.

XLA is one of 400 types of PI, and it was one of the first types of PI to be identified. It’s sometimes called Bruton’s agammaglobulinemia, after the man who discovered it, or congenital agammaglobulinemia.

There are over 450 different types of PI, each with its own characteristics and challenges.
Need a crash course? Learn the basics of PI.

The mutated gene responsible for XLA is located on the X chromosome. Since XLA is an X-linked disorder, only boys are affected. However, there is an immunodeficiency in girls that looks just like XLA. The deficiency seen in girls is called autosomal recessive agammaglobulinemia (ARA). The genes responsible for ARA are not on the X chromosome but cause a deficiency similar to XLA.

X-linked recessive inheritance

With X-linked recessive inheritance, the disease is passed on from mothers to sons. Because the mutation occurs in the genes on the X chromosome, males are affected by the disease, while females generally do not experience symptoms and are healthy. This is because males only carry one X chromosome. Females, on the other hand, carry two X chromosomes. Even though they carry the gene on one X chromosome, they also carry a normal gene on the other X chromosome.

Symptoms of XLA

People with XLA develop frequent infections involving the:

sinuses
ears
lungs

They may also develop infections of the bloodstream and internal organs. Gastrointestinal and skin infections can also be a problem.

Doctors may find that people with XLA have very small tonsils and lymph nodes (glands of the neck). This is because tonsils and lymph nodes are made up of B lymphocytes. In people with XLA, the size of these tissues are reduced because of the absence of B lymphocytes.

Diagnosis of XLA

Doctors may suspect XLA or ARA in people with small or absent tonsils and lymph nodes who experience repeated or severe bacterial infections.

To screen for XLA, a blood test is used to look for immunoglobulins, because most people with XLA do not have immunoglobulins, or have only small amounts. Another blood test will be used to test the percentage of B cells in the blood, because B cells are not produced in people with XLA. A low B cell count in the blood is the most reliable indicator of XLA or ARA.

Diagnosis can be confirmed by establishing the absence of a protein called Bruton’s tyrosine kinase (BTK), which is associated with XLA, or by finding an abnormality in the BTK gene.

What should I know about treatment for XLA?

You are not alone, but no one is quite like you. It's important to learn about the various treatments for PI, and should be individualized to meet your specific needs. Your healthcare team is there to provide recommendations based on you, and your situation. Here are some tips:

Keep track of how you’re doing and share the information with your doctor on a regular basis.
Your doctor will only know how you’re doing if you tell them. If you have questions, concerns, thoughts or feelings—speak up and share!
You and your doctor both play a part in managing your health. You can take an active role by learning as much as you can and by following your doctor’s recommendations.