Causes

Many primary immunodeficiency disorders are inherited — passed down from one or both parents. Problems in the genetic code that acts as a blueprint for producing the cells of the body (DNA) cause many of the immune system defects.

There are more than 300 types of primary immunodeficiency disorders, and researchers continue to identify more. They can be broadly classified into six groups based on the part of the immune system that's affected:

• B cell (antibody) deficiencies
• T cell deficiencies
• Combination B and T cell deficiencies
• Defective phagocytes
• Complement deficiencies
• Unknown (idiopathic)