What is the most common humoral immune deficiency disease?

Selective IgA deficiency is recognized as the most common humoral immune deficiency disease. This condition predominantly results in a deficiency of immunoglobulin A (IgA), which is an essential antibody found in mucosal areas, such as the gut, respiratory tract, and urogenital tract, as well as in secretions like saliva, tears, and breast milk. Individuals with this deficiency may have an increased susceptibility to infections, particularly those of mucosal surfaces.

The significance of selective IgA deficiency lies in its relatively higher prevalence compared to other humoral immune deficiencies. It is often diagnosed incidentally during routine testing for immunoglobulins, or when patients present with recurrent infections. Importantly, many individuals with this deficiency may remain asymptomatic and only require monitoring rather than active treatment.

In contrast, other conditions listed, such as common variable immunodeficiency, Bruton's agammaglobulinemia, and Wiskott-Aldrich syndrome are less common overall. Common variable immunodeficiency involves low levels of multiple types of immunoglobulins and typically presents later in life, while Bruton's agammaglobulinemia is a X-linked condition resulting in profoundly low levels of all immunoglobulin classes, primarily affecting males. Wisk