NCIt definition : A broad classification of dysgammaglobulinemias characterized by low or undetectable
serum levels of one of the five immunoglobulin classes. Deficiencies of immunoglobulins
present variably according to isotype. Selective deficiencies may be caused by decreased
or inefficient production from progenitor B cells without any corresponding decreases
in the other isotypes. The clinical course and prognosis is dependent upon the severity
of the selective deficiency and associated morbidity.;