IGHE and isolated agammaglobulinemia: However, it is worth noticing that few patients in the Ig replacement therapy group (e.g., with X-linked agammaglobulinemia, CVID) might have a deficiency of other antibody classes, including IgE; however, there were also patients with other conditions, such as IgG subclass deficiency/Nijmegen breakage syndrome/ataxia–telangiectasia, in that group (IRT+).