X-linked agammaglobulinemia

Background

A primary immunodeficiency that causes agammaglobulinemia
X-linked recessive, so almost all cases are men
- An autosomal recessive form exists called autosomal recessive agammaglobulinemia
One of the most common pediatric primary immunodeficiencies, though delayed presentations are possible
- Average age of diagnosis is 2.5 years, with majority of cases diagnosed by 5 years

Mutation of Bruton's tyrosine kinase (Btk) gene on the X chromosome at Xq21.3-Xq22
Mutation prevents B cell maturation
Many, many mutations exist

Commonly present with recurrent upper respiratory tract infections, including sinusitis and otitis media
- Onset of infections is typically around 6 to 9 months after maternal antibodies have dissipated
Infections may be particularly severe or require admission and intravenous antibiotics
Recurrent infections with encapsulated bacteria (Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae)
Increased risk of enterovirus infections
Increased risk of chronic diarrhea (particularly from Giardia duodenalis)