Selective IgG Subclass Deficiency

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IgG subclass deficiency

Definition and Characteristics

There are four human IgG subclasses, IgG1, IgG2, IgG3 and IgG4. Selective IgG subclass deficiency implies that an individual lacks one or several of these subclasses whereas levels of other immunoglobulin classes and subclasses are within the normal range. The deficiencies are most often relative rather than absolute. The total IgG level in patients with selective IgG subclass deficiency is most often normal.


Selective IgG deficiency is more common than other types of immunodeficiency. However, its frequency varies in different populations. Males and females are equally affected. Generally, selective IgG1 deficiency is very rare. Selective IgG2 and IgG3 deficiencies are more common in children and adults respectively.


No determinant gene has yet been identified. In some cases, the deficiencies are found to be due to deletion or mutation of the corresponding γ genes or mutation in th ...