Impaired antigen receptor rearrangement, with rare ‘leaky’ recombination events, leads to expansion of autoreactive oligoclonal T cells, eosinophilia, and markedly elevated IgE (Omenn, 1965; Villa et al., 2008; Villa et al., 1998; Villa et al., 2001; Wada et al., 2005). Here, IGHE is linked to Increased total eosinophil count.