Common Variable Immunodeficiency: A Comprehensive Guide

What is common variable immunodeficiency?

Common variable immunodeficiency (CVID), also known as common variable immune deficiency and humoral immunodeficiency, is a primary immunodeficiency disorder characterised by low levels of serum immunoglobulins (IgG, IgA, and/or IgM) together with antibodies directed at specific antigens. It affects B-cell differentiation into plasma cells, impairing antibody production despite normal or near-normal numbers of circulating B cells.

CVID is the most common symptomatic primary immunodeficiency in adults, with an estimated prevalence of 1 in 25,000 to 1 in 50,000 individuals. Although ‘common’ in name, it presents a wide clinical spectrum from mild recurrent infections to severe complications like autoimmunity, granulomatous disease, and malignancy. Memory B cells, crucial for long-term immunity, are often reduced or dysfunctional, leaving patients vulnerable to recurrent bacterial infections.

Who gets common variable immunodeficiency (CVID)?

CVID typically manifests between ages 20 and 40 but can present at any age, including childhood or later adulthood. It affects males and females equally, unlike some other immunodeficiencies. About 10 60% of cases have a genetic basis, with familial clustering in 10 20%. Sporadic cases predominate, potentially triggered by environmental factors like infections in genetically susceptible individuals.

• Genetic risk factors: Mutations in genes like TACI, BAFF-R, ICOS, and others impair B-cell function or T-cell regulation of B cells.
• Age distribution: Peak diagnosis 20 60years; paediatric onset in 20%.
• Familial patterns: Autosomal dominant or recessive inheritance in identified genetic cases.

What causes common variable immunodeficiency?

The precise aetiology of CVID remains multifactorial. Genetic variations in multiple genes disrupt B-cell maturation into plasma cells and antibody production. No single mutation accounts for all cases; over 30 genes are implicated, affecting B-cell development, survival, and T-cell help.

Key mechanisms include:

• Defective B-cell differentiation and plasma cell formation.
• Impaired T-cell regulation of humoral immunity.
• Environmental triggers (e.g., viral infections) unmasking genetic susceptibility.

In 70 60% of patients, no specific genetic cause is identified, suggesting complex polygenic or epigenetic factors.

What are the clinical features of common variable immunodeficiency?

CVID’s hallmark is recurrent infections due to antibody deficiency, but non-infectious complications affect 20 60% of patients.

Infections

Recurrent bacterial infections predominate, especially sinopulmonary:

• Sinusitis, otitis media, bronchitis (80 60–90%).
• Pneumonia (up to 50%), risking bronchiectasis.
• Gastrointestinal: Giardia, Campylobacter, norovirus causing chronic diarrhoea (20 60–50%).
• Skin/soft tissue, urinary tract infections.

Viral infections (e.g., herpes zoster) and vaccines are poorly controlled; live vaccines are contraindicated.

Non-infectious complications

• Autoimmunity (20 60–25%): Immune thrombocytopenia (ITP), autoimmune haemolytic anaemia (AIHA), rheumatoid arthritis-like disease, thyroiditis, vitiligo.
• Gastrointestinal (20 60–40%): Chronic diarrhoea, malabsorption, nodular lymphoid hyperplasia, inflammatory bowel disease-like enteropathy.
• Lymphoproliferation: Lymphadenopathy, splenomegaly (30%).
• Granulomatous disease: Lung, skin, liver (10 60–20%).
• Malignancy risk: Lymphoma (10%), gastric cancer.
• Lung damage: Bronchiectasis, interstitial lung disease.

How is common variable immunodeficiency diagnosed?

Diagnosis requires low IgG (at least 2 SD below normal) plus low IgA or IgM, poor vaccine responses, and exclusion of secondary causes. Age >4 years at testing.

Investigations

• Laboratory: Immunoglobulins, B/T-cell subsets (low switched memory B cells <2%).
• Vaccine challenge: No response to protein/polysaccharide antigens.
• Imaging: CT chest/sinuses for bronchiectasis/sinusitis.
• GI: Endoscopy/biopsy for enteropathy.
• Genetic testing: Targeted panels for known genes (10 60–30% yield).

What is the differential diagnosis for common variable immunodeficiency?

• Other primary immunodeficiencies: XLA, selective IgA deficiency, hyper-IgM syndrome.
• Secondary hypogammaglobulinaemia: Drugs (rituximab), malignancy (CLL), protein-losing enteropathy.
• Good syndrome (thymoma + hypogammaglobulinaemia).

What is the treatment for common variable immunodeficiency?

Lifelong immunoglobulin replacement is cornerstone therapy, reducing infection frequency by 50 60–70%.

Immunoglobulin replacement

• IVIG: 400 600 mg/kg every 3 64 weeks.
• SCIG: Weekly subcutaneous, preferred for stable patients.
• Monitors: IgG trough levels, infections.

Supportive care

• Antibiotics: Prophylactic (azithromycin) or therapeutic for infections.
• Autoimmunity: Steroids, rituximab, splenectomy (cautiously).
• GI: Metronidazole for Giardia, nutritional support.
• Lung: Physiotherapy, bronchodilators for bronchiectasis.

What is the outcome for common variable immunodeficiency?

With early diagnosis and IgRT, life expectancy approaches normal, though complications reduce it by 10 60–20 years in severe cases. Mortality from infections (pre-treatment), lymphoma, lung disease. Regular monitoring improves outcomes.

Prevention of complications

• Early IgRT initiation.
• Prophylactic antibiotics for bronchiectasis.
• Cancer screening: EGD, lymphoma vigilance.
• Vaccinations: Inactivated only (pre-IgRT).
• Lifestyle: Hygiene, nutrition, avoid live vaccines.

Immunisation

Inactivated vaccines (pneumococcal, influenza, COVID-19) recommended before or alongside IgRT, though responses are impaired. Avoid live vaccines (MMR, varicella, oral polio).

Related topics

• X-linked agammaglobulinaemia
• Selective IgA deficiency
• Hypogammaglobulinaemia
• Primary immune deficiencies

Frequently Asked Questions (CVID)

What is the most common presentation of CVID?

Recurrent sinopulmonary bacterial infections (sinusitis, pneumonia, otitis).

When should CVID be suspected?

In adults/children with unexplained recurrent infections plus low IgG/IgA.

Is CVID curable?

No, but immunoglobulin replacement therapy effectively manages it lifelong.

Does CVID increase cancer risk?

Yes, particularly lymphoma (10%) and gastric cancer.

Can CVID patients receive live vaccines?

No, due to antibody deficiency risking disseminated infection.

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Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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