The Primary Immunodeficiencies

Selective Deficiency of Other Immunoglobulin IsotypesAs techniques have become available, isolated deficiencies of each immunoglobulin isotype or subclass have been described. Perhaps the best known is IgM deficiency, which has been associated with meningococcemia and other severe or recurrent infections.74,75 The decrease in serum IgM levels may not be primary in all instances. Patients with gluten enteropathy, for example, may have a marked isolated IgM deficiency that resolves on treatment with a gluten-free diet.76 From the viewpoint of immunobiology, the selective absence of IgM is difficult to explain, since IgM synthesis and secretion precede production of IgG and IgA. . . .