Immunoglobulin heavy chain deficiency

Immunoglobulin heavy chain deficiency is a rare primary immunodeficiency disorder caused by deletions or mutations in the immunoglobulin heavy chain (IGH) gene cluster located on chromosome 14q32.33. The IGH locus encodes the heavy chain components of antibodies (immunoglobulins), including IgG subclasses (IgG1, IgG2, IgG3, IgG4), IgA (IgA1, IgA2), IgM, IgD, and IgE. Depending on the extent and location of the genetic deletion, patients may lack one or more immunoglobulin classes or subclasses. This condition primarily affects the immune system, impairing the body's ability to mount effective humoral (antibody-mediated) immune responses against infections. Clinical presentation is highly variable. Some individuals with immunoglobulin heavy chain deletions remain clinically asymptomatic, particularly when the deletion involves only one or two subclasses and compensatory antibody production is sufficient. However, others may experience recurrent sinopulmonary infections (such as pneumonia, sinusitis, and otitis media), bronchiectasis, and increased susceptibility to encapsulated bacterial organisms. The severity of symptoms generally correlates with the extent of the heavy chain gene deletion and the degree of immunoglobulin deficiency. Management depends on the clinical severity. Asymptomatic individuals may require only monitoring, while patients with significant antibody deficiency and recurrent infections may benefit from immunoglobulin replacement therapy (intravenous or subcutaneous immunoglobulin). Prophylactic antibiotics may also be used in some cases. Early diagnosis through immunoglobulin level measurement and genetic testing of the IGH locus is important for appropriate management and genetic counseling.

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