WHAT IS IT?
Bruton agammaglobulinemia (XLA) is a deficiency of immunoglobulins that is caused by a defect in the BTK gene (Bruton tyrosine kinase) that is responsible for B-cell maturation. When this gene is inactive B-cells do not mature, and then Ig antibodies of all types are not made. This is an X-linked condition.
WHY IS IT A PROBLEM?
This mutation leads to the absence of germinal centers and lymphoid follicles in lymph nodes, that lead to improper B-cell maturation. Without proper B-cell maturation the patient is unable to make antibodies and is severely immunocompromised.
WHAT MAKES US SUSPECT IT?
Risk factors: male (X-linked)
Recurrent ear infections: such as otitis media
Recurrent bacterial, enterovirus (i.e. polio or cocksackievirus), and Giardia lamblia infections after first 6 months post birth (this is when the maternal antibodies run out in newborns)
**Significantly decreased or absent tonsils and cervical lymph nodes in setting of recurrent otitis may suggest X-linked agammaglobulinemia (XLA)
HOW DO WE CONFIRM A DIAGNOSIS?
Complete blood count (CBC)
- Very low B cells
- Severe neutropenia seen in some patients
Serum Ig levels: decreased Ig levels of all types
- IgG typically between 100-200 mg/dL
- IgM typically < 20 mg/dL
- IgA typically < 20 mg/dL
Antibody titers to vaccine antigens (tetanus, H. influenzae, S. pneumoniae) show no antibodies
Immunofluorescence or Western blot shows no BTK protein in monocytes
Molecular genetic testing for BTK gene
HOW DO WE TREAT IT?
Regular immunoglobulin treatment – typical dose 400 mg/kg IV every 4 weeks or 100 mg/kg subcutaneously every week
HOW WELL DO THE PATIENTS DO?
The prognosis is generally favorable if the condition is caught early on in life, however ~10% of patients will develop significant infection even despite treatment.
WAS THERE A WAY TO PREVENT IT?
No, this is a genetic condition.
WHAT ELSE ARE WE WORRIED ABOUT?
Patients with this condition must avoid live vaccines (i.e. polio vaccine) due to their complete absence of antibodies/Igs.
OTHER HY FACTS?
After maternal IgG antibody levels go down (6 months post birth) children with this condition will typically develop enteroviral infections.
ARCHIVE OF STANDARDIZED EXAM QUESTIONS
This archive compiles standardized exam questions that relate to this topic.
Page Updated: 02.04.2016