Primary immunodeficiency disorders — also called primary immune disorders or primary immunodeficiency — weaken the immune system, allowing infections and other health problems to occur more easily. Many people with primary immunodeficiency are born missing some of the body's immune defenses, which leaves them more susceptible to germs that can cause infections.
Primary immunodeficiency diseases (PI) are a group of more than 250 rare, chronic disorders in which part of the body’s immune system is missing or functions improperly. While not contagious, these diseases are caused by hereditary or genetic defects, and, although some disorders present at birth or in early childhood, the disorders can affect anyone, regardless of age or gender. Some affect a single part of the immune system; others may affect one or more components of the system.
Some forms of primary immunodeficiency are so mild they may go unnoticed for years. Other types are severe enough that they're discovered almost as soon as an affected baby is born. Treatments can boost the immune system for many types of primary immunodeficiency disorders. Most people with the condition lead relatively normal, productive lives.