Divided into primary and secondary disorders.
Primary immunodeficiency disorders are almost always genetic in etiology.
Secondary immunodeficiency states may be related to infections, malnutrition, advanced age, immunosuppressive agents, radiation exposure, chemotherapy and autoimmune diseases.
Adaptive immunity defects can be sub classified on the basis of B or T cell abnormalities or both.
Most primary immunodeficiency processes manifest during infancy because of recurrent infections between 6 months and 2 years.