The body’s first line of defense against infectious diseases (like bacteria, viruses, or fungi) is the immune system. The specialized cells and organs of the immune system help identify and fight off these foreign pathogens. If the immune system is not working properly it can lead to several serious disorders like allergies, asthma, autoimmune diseases, or immune deficiency. Immune deficiency disorders lead to an abnormally low resistance to infection.
The immune system may be suppressed by medications or illness (most commonly). A primary Immune deficiency (PIDD) is present from birth as a genetic disorder that prevents the immune system from functioning properly. Examples of immune deficiency diseases include severe combined immune deficiency, common variable immune deficiency, Human immunodeficiency virus / acquired immune deficiency syndrome (HIV/AIDS), drug-induced immune deficiency, and graft versus host syndrome. An estimated 500,000 Americans are afflicted with PIDDs; 5,000 to 10,000 are severely affected. There are over 150 different forms of PIDDs; almost all of these diseases are considered rare (affecting fewer than 200,000 people in the United States).