X-linked agammaglobulinemia

Gene : BTK

What is X-linked agammaglobulinemia?

X-linked agammaglobulinemia (XLA) is an inherited disorder that affects the immune system. Affected individuals are unable to produce enough antibodies, which are the part of the immune system that attaches itself to the invading bacteria and mark them for destruction by the rest of the immune system. Infants are protected for the first few months of life due to the transfer of antibodies from mom to fetus through the placenta. Once the maternal supply has diminished, the infections become more common. The most common illnesses are ear infections, pink eye, pneumonia and sinus infections. Because their immune system is so poor, these can become life-threatening infections. Affected individuals are also more susceptible to infections that cause chronic diarrhea. There is no cure for XLA, however with extreme care during times of illness and regular gammaglobulin treatments, quality of life is improved and life expectancy is near normal for affected individuals. XLA is caused by pathogenic variants in the BTX gene.

How is X-linked agammaglobulinemia inherited?

Adrenoleukodystrophy is inherited in an X-linked recessive manner. This type of inheritance requires the presence of one copy of a pathogenic variant in the gene located on the X-chromosome for males to be affected. When the pathogenic variant is inherited from the unaffected carrier mother, the male child will have the genetic disease. There is a 50% chance that a baby will inherited the pathogenic variant from the mother; females who inherited the pathogenic variant will be carriers, males who inherited the pathogenic variant will be affected.

What does it mean to be a carrier?

There are generally no signs or symptoms associated with being a carrier for XLA. However, the risk to have a child affected with XLA is increased for female carriers.

How common is X-linked agammaglobulinemia?

XLA is estimated to affect 1 in 100,000 male newborns worldwide.

Family References and Resources
Clinician References
What is Analyzed?
  • Full gene sequencing
Affected Systems


Carrier Rates
Detection Rate
Carrier Frequency
General Population 92% 1 in 250000

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