2 per 100,000 poulation
Multiple possible defects (not X-linked) - hypogammaglobulinaemia (IgG, usually IgA, possibly IgM)
lack of antibodies to neutralise & opsonise pathogens → severe, persistent, unusual & recurrent infections & autoimmune, malignant, enteric & lymphoid disorders
Patients present with clinical features of infections:
Streptococcus pneumoniae (LRTIs & septicaemia)
Haemophilus influenzae (URTI/LRTIs & meningitis)
Neisseria meningitidis (meningitis & septicaemia) Staphylococcus aureus (skin & soft tissueinfections)
Pseudomonas aeruginosa (ear infections & LRTIs)
Giardia lamblia (intestinal infection)
most common sites are ears & respiratory tract