We found 4/83 (4.8%) patients with both low IgM and IgG, and the risk of infection in these patients is considered to be more strongly linked to the low IgG, though some studies show that low IgM in association with low IgG can be associated with increased risk of infection-related chronic lung disease/bronchiectasis [15]. The gene discussed is CD40LG; the disease is bronchiectasis.