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. (sino-pulmonary 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.

CVID can be associated with autoimmune disorders that affect other blood cells causing low numbers of white cells or platelets, anemia, arthritis, and other conditions such as endocrine disorders.  Gastrointestinal problems including chronic diarrhea, weight loss, nausea, vomiting, and abdominal pain can also be present. In some forms of CVID, patients develop granulomas in the lungs, lymph nodes, liver, skin, or other organs.

People with CVID are also at an increased risk for certain cancers (lymphoid and gastrointestinal cancers primarily).

Treatment for CVID involves lifelong immunoglobulin replacement, preventative antibiotics, and if indicated management of autoimmune and granulomatous disease.