Common Variable Immunodeficiency

Excerpt

Common variable immunodeficiency (CVID) represents the most common symptomatic primary immunodeficiency worldwide. The disorder arises from impaired antibody production caused by defects in B cell differentiation and function, often accompanied by abnormalities in T cell compartments and immune regulation. Rather than constituting a single disease, CVID encompasses a heterogeneous group of conditions unified by hypogammaglobulinemia—characterized by reduced serum levels of IgG, typically decreased IgA, and occasionally low IgM—together with poor or absent specific antibody responses to immunizations or infections.

CVID displays marked variability in both clinical and immunological features. Patients frequently present with recurrent sinopulmonary infections, autoimmune manifestations, granulomatous inflammation, increased susceptibility to malignancy, and impaired antibody responses despite a normal or near-normal circulating B cell count. The syndrome arises from a spectrum of genetic abnormalities, many of which remain unidentified. The term "variable" highlights the disorder’s broad range of clinical presentations and underlying molecular mechanisms.