In a series of 44 patients with IgE levels lower than 2.5 kU/L, of which 57% had depressed serum levels of other immunoglobulins, arthralgias, chronic fatigue, and symptoms suggestive of airway infection, autoimmune diseases were more frequent than among patients with IgE levels higher than 2.5 kU/L [42]. Here, IGHE is linked to autoimmune disease.