Common variable immune deficiency (CVID) is a genetic disorder characterized by a weakened immune system. Patients with CVID frequently suffer from infections.
What is CVID?
CVID is a primary immunodeficiency disease that primarily causes a reduction in the blood antibody levels. Since antibodies are required to fight against harmful microorganisms, including bacteria and viruses, people with CVID mostly have weaker immunity and are predisposed to repeated infections. CVID-related infections mostly occur in the lungs, sinuses, ears, and digestive system.
Human antibody molecule illustration. Credit: YuriiHrb / Shutterstock
In CVID, enlargement of the spleen (splenomegaly) or lymph nodes (lymphadenopathy) can occur due to excessive buildup of immune cells. Such accumulation can also occur in other organs, leading to the formation of small lumps.
Autoimmune disorders are among common comorbid conditions, affecting about 25% of CVID patients. The most common autoimmune disorders include immune thrombocytopenia (a type of bleeding disorder developed due to reduced platelet number) and autoimmune hemolytic anemia (early death of RBCs).
People with CVID are more likely to develop immune system-related cancers, such as non-Hodgkin lymphoma. In addition, gastric infection or inflammation can lead to cancers of the gastrointestinal tract.
What is the prevalence of CVID?
CVID is a relatively rare condition, affecting about 1 in 25,000 individuals globally. Both males and females are equally affected by the condition. Although it occurs in children or teens, the condition mostly remains undetected until adulthood. The disease is frequently detected when people are in their twenties or thirties.
What are the causative factors?
Although the exact etiology is unknown, both exogenous (environmental) and endogenous (genetic) factors are believed to be responsible for the development of CVID.
Regarding genetic factors, CVID is primarily caused by genetic mutations associated with abnormal growth and activity of B cells, which are specialized immune system cells for producing antibodies.
The impaired B cells are unable to produce a sufficient number of antibodies, leading to reduced ability to fight infections. So far, scientific studies have identified 13 genes; of them, TNFRSF13B is the most frequently mutated gene that encodes a protein responsible for the proper development of B cells. However, mutations in 13 genes are associated with only 10% of all CVID cases.
The cause of CVID in the other 90% of patients is still unknown. People with CVID are mainly deficient of three types of antibodies, namely immunoglobulins G, A, and M.
How CVID is inherited?
In most cases, CVID patients are without any family history of the disease (sporadic). However, in some rare cases, the condition follows an autosomal recessive inheritance pattern, meaning that two mutated genes must be inherited to develop the disease.
An autosomal dominant inheritance pattern can also be observed in a few cases, which means a mutation in a single gene copy is enough to trigger the disease onset.
What are the common symptoms?
The intensity of CVID symptoms, which typically range from mile to severe, vary from person to person.
The most common symptoms include breathing difficulty, chronic cough, ear infections, sinusitis, and lung infections (pneumonia). In some cases, inflammation can occur in the knee, ankle, elbow, or wrist joints.
The infections in the gastrointestinal tract often result in diarrhea and weight loss. In addition, repeated infection in the lungs can lead to bronchiectasis, which is characterized by widening of the lung airways, leading to excessive mucus accumulation and further lung infection.
How is CVID diagnosed?
Initial diagnosis records the medical history of recurrent infections. An unusual response to certain vaccines is also sometimes considered as a possible diagnostic marker. CVID patients mostly remain unresponsive to vaccination against certain diseases, including measles and influenza, as they are unable to produce an antibody response.
To confirm the diagnosis, doctors may ask for blood tests to check the level of immunoglobulins or the number of B cells in the blood.
How is CVID treated?
The standard of care for CVID treatment is immunoglobulin replacement therapy, which should be continued at regular intervals throughout life. The treatment involves intravenous or subcutaneous administration of antibodies obtained from healthy donors to the affected person.
In addition, doctors prescribe antibiotics to treat the infections caused by CVID. In some cases, the clearance of airway secretions is also helpful. To treat autoimmune diseases, corticosteroid therapy can be used. However, corticosteroids can themselves cause immune suppression.