• A 6-year-old boy presents to the hospital with a severe upper respiratory infection requiring  hospitalization. Chart review reveals that he has presented multiple times to the emergency room and primary care physician’s office for a variety of infections, including otitis media, upper respiratory infections, pneumonia, and sinusitis. When detailing family history, it is found that his maternal uncle died of an infection as a child. Lab findings include decreased levels of IgG, IgM, and IgA.
  • Primary humoral immunodeficiency characterized by decreased immunoglobulins
  • Genetics
    • X-linked recessive
      • seen in male children
  • Pathogenesis
    • defect in Bruton tyrosine kinase (BTK)
    • defective maturation of B-cells
      • impaired signaling from pre-B-cell receptor 
      • ↓ B-cells
      • ↓ production of all classes of Ig
    • impaired antibody immune response
  • Symptoms
    • recurrent infections
      • especially after 6 months old (↓ maternal IgG)
      • Streptococcus pneumoniae, Hemophilus influenzae, Streptoccocus 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)
  • Diagnosis based on family history, clinical history, and exam
  • Serologies
    • ↓ all classes of Ig
    • ↓ levels of B-cells
    • normal T-cells
  • Diagnosis confirmed with DNA, mRNA, or protein analysis showing mutation in BTK
Differential Diagnosis
  • Common variable immunodeficiency
  • Severe combined immunodeficiency
  • Transient hypogammaglobulinemia of infancy
  • Antibiotics for infections
  • Regular IVIG infusions
Prognosis, Prevention, and Complications
  • Prognosis
    • normal prognosis with regular IVIG therapy and early detection
  • Prevention
    • screening in newborns
    • regular IVIG to prevent infections
  • Complications
    • small risk of malignancy

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