Abstract
This chapter provides a brief overview of major primary and acquired immunodeficiency disorders of the human immune system. It aims to assimilate information regarding immunodeficiency diseases, their current classification, causes and treatment options. Immunodeficiency diseases are a major cause of mortality and morbidity. These diseases result from the malfunction of the immune system and this malfunction can stem from many causes. The International Union of Immunological Societies Expert Committee on Primary Immunodeficiency has reviewed the classification of Primary immunodeficiency diseases every 2 years since its inception in 1973. Human severe combined immunodeficiency (SCID) was first reported by Swiss workers more than 50 years ago. X-linked recessive severe combined immunodeficiency is the most common form of SCID and accounts for roughly 46% of the cases in the United States. Common variable immune deficiency as a heterogeneous group of primary immune deficiencies is characterized by insufficient serum levels of immunoglobulins, reduced response to specific antigens and higher incidence of repeated infections.