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X-linked agammaglobulinemia (Bruton's disease)
Last reviewed: 04.07.2025
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X-linked agammaglobulinemia is characterized by low or absent levels of immunoglobulins and antibodies, absence of B lymphocytes, which is manifested by recurrent infections caused by encapsulated bacteria.
What causes X-linked agammaglobulinemia?
X-linked agammaglobulinemia results from a mutation in the X-chromosome gene encoding Bruton tyrosine kinase (BTK). BTK is essential for the development and maturation of B lymphocytes; without it, neither B lymphocytes nor antibodies are formed. As a result, boys have very small tonsils and do not develop lymph nodes; the clinical picture is characterized by recurrent purulent infections of the lungs, paranasal sinuses, and skin with encapsulated bacteria (Streptococcus pneumoniae, Hemophilus influenzae). There is a tendency to persistent CNS infections as a result of vaccination with live oral polio vaccine, Echovirus, and Coxsackievirus; these infections may manifest as progressive dermatomyositis, with or without encephalitis.
Diagnosis of X-linked agammaglobulinemia
Diagnosis is based on low IgG levels (< 100 mg/dL) and absent B lymphocytes (< 1% CD19+ cells by flow cytometry). Transient neutropenia may also be present. If there is an identical disease in family members, chorionic villus sampling, amniocentesis, or cord blood sampling are performed for prenatal diagnosis.
[ How is X-linked agammaglobulinemia treated?
Treatment consists of intravenous administration of immunoglobulin 400 mg/kg/month. It is important to prescribe adequate antibiotic therapy for each infectious process; in case of bronchiectasis, long-term treatment with a change of antibiotics is necessary. In case of early diagnosis and appropriate treatment, the prognosis is favorable if viral infections of the central nervous system do not develop.