Common variable immune deficiency

Common variable immune deficiency (CVID) is a disorder that damages the immune system. Because their immune system cannot adequately protect them, people with CVID can develop recurrent infections in the lungs, sinuses, or ears. Over time, recurrent lung infections can lead to chronic lung disease and life-threatening breathing problems. Most people with CVID also have pneumonia at least once in their life. Affected individuals may also experience gastrointestinal problems, such as infections or inflammation. These problems can cause bloating, diarrhea, decreased absorption of nutrients, and weight loss. For reasons that are unclear, some people with CVID have enlarged lymph nodes or an enlarged spleen (splenomegaly).

Approximately 20 percent of people with CVID have an autoimmune disorder, which occurs when the immune system malfunctions and attacks the body's tissues and organs. The autoimmune disorder most commonly seen in people with CVID is immune thrombocytopenia purpura. This condition is characterized by a reduced number of platelets in the blood, which leads to abnormal bruising and bleeding. Individuals with CVID also have a somewhat higher than normal risk of developing certain types of cancer, including cancer of immune system cells called non-Hodgkin lymphoma. Some studies have found an increased risk of developing stomach cancer in people with CVID.

People with CVID may start experiencing signs and symptoms of the disorder in childhood or adolescence, but the majority of affected individuals do not experience immune problems related to CVID until adulthood.

The exact prevalence of CVID is unknown. It is estimated to affect 1 in 25,000 to 1 in 50,000 people.

CVID is believed to result from mutations in genes that are involved in the development and function of B cells. B cells are specialized white blood cells that help protect the body against infection. When B cells mature, they produce special proteins called antibodies (which are also known as immunoglobulins). These proteins attach to specific foreign particles and germs, marking them for destruction. Mutations in the genes associated with CVID result in dysfunctional B cells that cannot make sufficient amounts of antibodies.

People with CVID have a shortage (deficiency) of specific proteins called immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM). The lack of certain antibodies makes it difficult for people with this disorder to fight off infections. In addition, vaccines do not provide protection for people with CVID because these individuals lack antibodies.

Mutations in at least five genes have been associated with CVID. Approximately 10 percent of affected individuals have mutations in the TNFRSF13B gene. Mutations in each of the other genes associated with CVID account for only a small percentage of cases.

In most cases of CVID, the cause is unknown.

Read more about the TNFRSF13B gene.

See a list of genes associated with common variable immune deficiency.

Most cases of CVID are classified as sporadic and occur in people with no apparent history of the disorder in their family. Although the cause of these cases is unclear, sporadic cases probably result from a complex interaction of environmental and genetic factors.

In a few families, CVID is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

In very rare cases, this condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

Not all individuals who inherit a gene mutation associated with CVID will develop the disease. In many cases, affected children have an unaffected parent who shares the same mutation.