Primary Immunodeficiency Diseases (PIDD) comprise a group of more than 100 diseases which are due to defects in the body’s defenses (immune system). These diseases affect thousands of infants, children, and adults in the United States.
In most cases, PIDD are associated with acute or recurrent infections depending on the portion of the immune system affected. Most PIDD are inherited in our genes, so they are present at birth, but they often do not become apparent or diagnosed until late in childhood, or even in adult life. It often takes time for a pattern of recurrent infections or other symptoms to develop before a PIDD is suspected. There are more than 100 different genetic causes of PIDD.