Selective deficiency of immunoglobulin G [IgG] subclasses

This code signifies a primary immunodeficiency characterized by abnormally low levels of one or more, but not all, immunoglobulin G (IgG) subclasses, despite normal total IgG and other immunoglobulin levels. Patients typically experience recurrent bacterial infections, particularly of the respiratory tract.

Assign this code when a patient presents with a documented selective deficiency of one or more IgG subclasses (e.g., IgG1, IgG2, IgG3, IgG4) confirmed by laboratory testing. This diagnosis is often made in individuals with a history of recurrent infections, especially sinopulmonary, who have normal total IgG, IgA, and IgM levels.

• Ensure laboratory results specifically identify which IgG subclass(es) are deficient.
• Do not use this code if total IgG is low; instead, consider codes for common variable immunodeficiency or other hypogammaglobulinemias.
• Code any associated recurrent infections separately as secondary diagnoses.