Updated: 5/15/2019

X-Linked Agammaglobulinemia

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Snapshot
  • A 3-year-old boy is brought to the pediatrician’s office for an ear infection. He has had multiple upper respiratory, ear, and skin infections since 6 months of age. He has required inpatient admissions to the pediatric ward twice for intravenous antibiotics. On physical exam, he has no tonsils and has no history of tonsillectomy. Levels of IgG, IgM, and IgA are decreased. Genetic testing is sent to confirm the diagnosis.
Introduction
  • Clinical definition
    • primary humoral immunodeficiency characterized by decreased immunoglobulins
  • Epidemiology
    • demographics
      • boys
  • Pathogenesis
    • defective maturation of B-cells
      • impaired signaling from pre-B cell receptor
      • ↓ B-cells
      • ↓ production of all classes of Ig
    • impaired antibody immune response
  • Genetics
    • X-linked recessive
    • defect in Bruton tyrosine kinase (BTK)
  • Prognosis
    • normal prognosis with regular intravenous immunoglobulin (IVIG) therapy and early detection
Presentation
  • Symptoms
    • recurrent infections
      • after 6 months of age 
        • due to decreased maternal IgG
      • Streptococcus pneumoniae, Hemophilus influenzae, Streptococcus pyogenes, and Pseudomonas
    • increased susceptibility to encapsulated bacteria and blood-borne viruses
      • due to opsonization defect
  • Physical exam
    • absent/scant lymphoid tissues
      • tonsils/lymph nodes
Studies
  • Diagnostic testing
    • studies
      • ↓ all classes of Ig
      • ↓ levels of B-cells
      • normal T-cells
  • Diagnostic criteria
    • confirmed with DNA, mRNA, or protein analysis showing mutation in BTK
Differential
  • Severe combined immunodeficiency
    • distinguishing factor
      • similarly presents with recurrent bacterial infections
      • unlike Bruton agammaglobulinemia, flow cytometry shows absent T-cells
  • Transient hypogammaglobulinemia of infancy
    • distinguishing factor
      • does not extend beyond infancy
Treatment
  • Management approach
    • mainstay of treatment is to treat each infection with antibiotics
  • First-line
    • intravenous immunoglobulin
Complications
  • Small risk of malignancy
 

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