BTK and common variable immunodeficiency: Interestingly, alterations in the regulation of secondary recombination events have been reported in BTK-, Interleukin-1 Receptor-associated Kinase 4 (IRAK4)-, and MyD88-deficient patients and in a group of Common Variable Immunodeficiency (CVID) patients with expanded autoreactive CD21−/low B cells (Ng et al., 2004; Isnardi et al., 2008; Meffre, 2011).