Common Variable Immunodeficiency

Introduction

Common variable immunodeficiency is a syndrome characterized by marked hypogammaglobulinemia.

It typically presents after an initial period of apparent normal immune function.
It is the most prevalent of all primary antibody deficiency defects.
The condition affects males and females with an almost equal sex distribution.

The disease is primarily a phenotypic diagnosis.

Most cases demonstrate a complex, polygenic inheritance pattern.
Patients often have normal numbers of circulating B cells.
Lymphoid cortical follicles are frequently present.
The core defect lies in the inability of blood B cells to differentiate normally into immunoglobulin-producing plasma cells.
This developmental block leads to a characteristic deficiency of switched memory B cells.

Genetic Variants	Associated Features
CTLA4	Pronounced lymphoproliferation and autoimmunity.
LRBA	Pronounced lymphoproliferation, enteropathy, and autoimmunity.
ICOS	Autoimmunity and neoplasia.
NFKB1 / NFKB2	Autoimmunity.
CD19 / CD20 / CD21 / CD81	Hypogammaglobulinemia.

Patients most commonly present with symptoms before 20 years of age. The clinical course is highly variable.

Recurrent sinopulmonary infections are the hallmark presentation.
- These include frequent episodes of sinusitis, otitis, and pneumonia.
Repeated pulmonary infections frequently result in bronchiectasis.
Patients have an increased risk of sepsis and meningitis.
- These severe infections are typically caused by encapsulated bacteria.
Enterovirus meningoencephalitis is notably rare, which distinguishes it from X-linked agammaglobulinemia.

A spruelike enteropathy is frequently observed.
Various autoimmune cytopenias can occur.
- Hemolytic anemia and thrombocytopenia are common manifestations.
Gastrointestinal autoimmunity includes gastric atrophy, achlorhydria, and pernicious anemia.
Alopecia areata may also develop.

Patients frequently present with enlarged tonsils and lymph nodes.
Splenomegaly is present in approximately 25% of patients.
Nodular lymphoid hyperplasia can affect the intestinal tract.
Noncaseating sarcoid-like granulomas can develop in multiple organs.
- When involving the lungs, it is termed granulomatous and lymphocytic interstitial lung disease.
There is a significantly increased risk for developing B-cell lymphomas.

Diagnosis requires specific criteria based on quantitative immunoglobulin levels and cellular analysis.

Diagnostic Parameter	Typical Findings
Immunoglobulin G (IgG)	Must be <2 standard deviations below the age-adjusted norms.
Immunoglobulin A (IgA)	Levels are typically low.
Immunoglobulin M (IgM)	Levels are typically low.
B Lymphocytes	Absolute counts may be normal or variable.
Memory B Cells	Decreased frequency of switched memory B cells is characteristic.

Therapy is centered on preventing infections and managing complications.

Lifelong immunoglobulin replacement therapy is the standard of care.
It can be administered via intravenous or subcutaneous routes.
This therapy significantly decreases the frequency of sinopulmonary infections.
Adequate dosing mitigates the progression of chronic lung disease and bronchiectasis.
However, immunoglobulin replacement does not improve autoimmune or lymphoproliferative complications.
- The presence of these complications confers a poorer prognosis.

Judicious use of appropriate antibiotics is required for documented acute infections.
Prophylactic antibiotics are frequently utilized in conjunction with immunoglobulin therapy.
- Macrolides, such as azithromycin, are often chosen for patients with chronic recurrent respiratory tract infections.

Specific biologic therapies are available for certain genetic variants.
- Abatacept (a CTLA4-Ig fusion protein) is successfully used for treating cytopenias and lymphoproliferation in patients with CTLA4 haploinsufficiency and LRBA deficiency.
Corticosteroids or other immunosuppressants may be required to manage severe autoimmune manifestations.