X-Linked agammaglobulinemia (XLA) is an inherited immunodeficiency in which the body is unable to produce the antibodies needed to defend against bacteria and viruses.
Frequently called Bruton's Agammaglobulinemia, XLA is caused by a genetic mistake in a gene called Bruton's tyrosine kinase (BTK), which prevents B cells from developing normally. B cells are responsible for producing the antibodies that the immune system relies on to fight off infection.
The most common bacteria causing infection in XLA are Streptococcus, Staphylococcus and Haemophilus.
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XLA often becomes apparent in infancy due to recurrent and severe bacterial infections including:
- Ear infections
- Diarrhea due to a parasite called Giardia
When a baby is first born, it is protected from infection by IgG antibodies that are passed through the placenta from the mother. This maternal IgG only lasts for several months, and then the infant needs to start producing antibodies on its own. When affected by XLA, the infant cannot do this on his own, and becomes susceptible to these recurrent infections.
XLA can be detected through screening tests that measure immunoglobulin levels or the number of B cells in the blood.
There is no cure for XLA, but the condition can be successfully treated. Immunoglobulin replacement therapy is a life-long and life-saving treatment that restores some of the missing antibodies. In addition, some people benefit from a daily course of oral antibiotics to prevent or treat infections.
Most individuals with XLA who receive immunoglobulin on a regular basis can lead relatively normal lives.
Live viral vaccines, such as those for polio, measles, mumps or rubella, are not considered safe for people with XLA. Though rare, these vaccines can infect the recipient with the very disease they were intended to prevent. This is true for most B and T cell immune defects.
To learn more about PIDDs visit the Immune Deficiency Foundation website.