NCIt definition : A broad classification of dysgammaglobulinemias characterized by low or undetectable
serum levels of immunoglobulin class G (IgG). Deficiencies of IgG present variably
according to subclass. IgG deficiencies are typically relative among subclasses and
not absolute. Thus even with a given selective IgG subclass deficiency, total IgG
levels may still fall within normal range. The clinical course and prognosis is dependent
upon the severity of the deficiency and associated morbidity.;