An immune disorder is a dysfunction of the immune system. These disorders can be characterized in several different ways:By the component(s) of the immune system affected By whether the immune system is overactive or underactive By whether the condition is congenital or acquired
According to the International Union of Immunological Societies, more than 150 primary immunodeficiency diseases (PIDs) have been characterized. However, the number of acquired immunodeficiencies exceeds the number of PIDs.
It has been suggested that most people have at least one primary immunodeficiency. Due to redundancies in the immune system, though, many of these are never detected.