Other than the physiologic hypogammaglobulinemia of infancy, 80% of the confirmed immunodeficiencies consist of four syndromes: transient hypogammaglobulinemia of infancy (THI), IgG subclass deficiency, partial antibody deficiency with impaired polysaccharide responsiveness (IPR), and selective IgA deficiency IgAD. None are life threatening, all can be readily managed, and many recover spontaneously. An exact incidence of these disorders is not known. A summary of immunodeficiency registries in four countries listed IgAD in 27.5% of the patients, IgG subclass deficiency in 4.8%, and THI in 2.3%. The 1999 US survey of primary immunodeficiencies conducted by the Immune Deficiency Foundation found that 17.5% of these patients had IgAD and 24% had IgG subclass deficiency, while THI and IPR were not listed. The Jeffrey Modell Foundation (2005) survey of their global centers in 2004 reported IgAD in 15.5%, subclass deficiencies in 8%, and THI in 2% of their patients.