X-Linked Agammaglobulinemia (XLA)
Description
X-Linked Agammaglobulinemia (XLA), also known as Bruton‘s agammaglobulinemia, is a rare, inherited disorder that primarily affects males. This condition disrupts the body‘s ability to produce antibodies, crucial for fighting infections. Individuals with XLA are highly susceptible to recurrent and severe bacterial infections, highlighting the importance of early diagnosis and effective management.
Genes Involved
XLA is caused by mutations in the BTK gene located on the X chromosome. This gene provides instructions for producing Bruton‘s tyrosine kinase (BTK), an enzyme critical for the development of B cells, which are responsible for antibody production.
Recognizing the Signs and Symptoms
The primary symptom of XLA is a severe deficiency in antibodies. This can lead to a wide range of recurring bacterial infections, including:
- Ear infections (otitis media)
- Pneumonia
- Sinusitis
- Meningitis
- Sepsis
- Gastrointestinal infections
- Skin infections
Infections may begin in early childhood, often around 6 months of age when the mother‘s antibodies transferred during pregnancy start to wane.
Causes
XLA is a genetic disorder caused by mutations in the BTK gene. These mutations disrupt the production of BTK, a crucial enzyme for B cell development. Without functional BTK, B cells cannot mature properly, leading to a severe deficiency in antibody production.
Inheritance/recurrence risk
XLA is inherited in an X-linked recessive pattern. This means that the defective gene is located on the X chromosome. Males, who have only one X chromosome, are affected by the condition if they inherit the mutated gene from their mother. Females, with two X chromosomes, are typically carriers of the condition. However, they can be affected if they inherit two copies of the mutated gene.
The risk of inheritance depends on the family history. If one parent is a carrier, there is a 50% chance of passing the mutated gene to their offspring. If both parents are carriers, there is a 25% chance that their child will be affected by XLA.
