Common Variable Immunodeficiency (CVID) is an antibody deficiency that leaves the immune system unable to defend against bacteria and viruses, resulting in recurrent and often severe infections primarily affecting the ears, sinuses, and respiratory tract. (sinopulmonary infections). In the majority of cases, the diagnosis is not made until the third to fourth decade of life. Permanent damage to the respiratory tract (bronchiectasis) may occur due to severe and repeated infections.
Although genetic mutations that lead to CVID have been identified, the exact cause and genetic inheritance pattern of CVID is unknown in most cases. Both males and females are affected. It is one of the most common forms of primary immunodeficiency disease (PIDD), and the severity of symptoms varies from one person with the disease to another.