Genetic immunodeficiency incidence is relatively low compared to acquire immunodeficiency.

Refers to a set of clinicolaboratory entities with varied causes and manifestations.

Includes deficiencies of humoral immunity.

Predisposition toward infections that normally are defended against by antibody responses and include Streptococcus pneumoniae and Haemophilus influenzae infections, which frequently involve the respiratory tract.

Immunoglobulins produced by B cells play a central role in humoral immunity.

May result from lack of production or an excessive loss of immunoglobulins, or both.

Congenital disorders can involve B-cell development can result in complete or partial absence of one or more Ig isotypes.

Defects that occur early in developmental stages may result in combined immunodeficiency involving all cell types, and defects further down the differentiation pathways may result in deficiencies of a single cell type only.

Acquired or secondary hypogammaglobulinemia usually involves medications, renal loss of immunoglobulins, gastrointestinal immunoglobulin loss, B-cell–related malignancies, and severe burns.

Renal loss of immunoglobulins is typified by nephrotic syndrome, in which IgG loss is usually accompanied by albumin loss.

Gastrointestinal loss of immunoglobulins occurs in protein-losing enteropathies and intestinal lymphangiectasia.

Increased catabolism of immunoglobulins occurs in various diseases, including the B-cell lineage malignancies and severe burns but also in dystrophic myotonia.

Humeral immunity deficiencies represent 50% of primary immunodeficiencies.

IgA deficiency is the most common antibody deficiency syndrome, followed by common variable immunodeficiency.

IgA deficiency incidence is one case in 700 persons of European ancestry.

Common variable immunodeficiency incidence is one case in 5-10,000 persons of European ancestry.

IgM deficiency is a rare disorder.

IgG4 deficiency is very common and is seen in 10-15% of the general population and is usually an asymptomatic process.

Results in recurrent infections with microorganisms primarily localized to the upper and lower airways, although bacteremia and GI infections can also occur.

In patients with associated defects in cellular immunity opportunistic viral, fungal, or parasitic infections may occur.

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