Which immunodeficiency disorder is characterized by low levels of all immunoglobulin classes?

Common variable immunodeficiency (CVID) is characterized by low levels of all immunoglobulin classes. This disorder leads to a significant reduction in the ability of the immune system to produce antibodies in response to infections, which is reflected in the low levels of IgG, IgA, and IgM. Individuals with CVID often suffer from recurrent infections, particularly with encapsulated bacteria, due to the lack of adequate humoral immunity.

CVID can present at any age and is associated with an increased risk for autoimmune disease and malignancies. The diagnosis is typically made after excluding other causes of hypogammaglobulinemia, and it often requires confirming the persistence of low antibody levels over time.

The other disorders mentioned are differentiated by specific antibody deficiencies or patterns of immunoglobulin levels. For example, X-linked agammaglobulinemia primarily affects males and results in virtually absent immunoglobulins due to a defect in B cell development, primarily affecting IgG. Selective IgA deficiency shows a decrease in only immunoglobulin A while leaving other classes intact. HyperIgM syndrome is characterized by elevated levels of IgM and low levels of IgG and IgA (with a defect in class switching), rather than a decrease