Question: What is (are) Common variable immunodeficiency ?
Answer: Common variable immunodeficiency (CVID) is a group of disorders in which the immune system cannot make antibodies against agents that cause infection (such as bacteria). CVID is characterized by low levels of most or all of the immunoglobulin (Ig) classes. This causes affected people to get frequent infections, particularly in the sinuses, lungs, and digestive tract. Symptoms most commonly begin in early adulthood but have been found in children as young as age two. While in most cases the cause of CVID is unknown, it has been associated with changes (mutations) in at least 10 genes. About 10% of cases are due to mutations in the TNFRSF13B gene. Treatment for CVID includes Ig replacement therapy, which stops the cycle of recurrent infections.
Source: GARD

Question: What causes Common variable immunodeficiency ?
Answer: What causes common variable immunodeficiency (CVID)? Common variable immunodeficiency (CVID) is usually sporadic and thought to result from a combination of genetic and environmental factors. In most cases, the exact cause of CVID is unknown. Genetic factors associated with CVID include mutations in genes involved in the development and function of immune system cells (B cells) which help protect against infection. B cells make proteins called antibodies (also known as immunoglobulins), which attach to foreign agents and "mark" them to be destroyed. Mutations in genes associated with CVID result in B cells that don't make enough antibodies. This causes difficulty fighting infections, causing the signs and symptoms of CVID. Mutations in at least 10 genes have been associated with CVID. About 10% of affected people have mutations in the TNFRSF13B gene. However, not all people who inherit a mutation associated with CVID develop the disease. This is why additional genetic and/or environmental factors are probably needed for the disorder to occur. While CVID usually occurs in people with no family history of the condition, some cases are inherited in an autosomal dominant or autosomal recessive manner.
Source: GARD

Question: What are the treatments for Common variable immunodeficiency ?
Answer: How might common variable immunodeficiency be treated? The main treatment for common variable immunodeficiency (CVID) is Ig replacement therapy, which stops the cycle of recurrent infections. Ig may be taken intravenously (through the vein) or subcutaneously (by injection). Adverse reactions to Ig must be monitored during therapy. Ig therapy is effective in most people, leading to less frequent infections and arthritic symptoms. However, gastrointestinal (digestive) symptoms have little improvement with IVIG. In some people wwith CVID and severe autoimmune disease, steroids or other immunosuppressive drugs in addition to Ig therapy may be needed. Detailed information about the management of CVID can be viewed on Medscape Reference's Web site.
Source: GARD