Also known as: Antibody deficiency, primary antibody deficiency, B-cell immunodeficiency, antibody production deficiency
Humoral immune deficiencies are a group of rare, inherited disorders that affect the immune system’s ability to make effective antibodies. Antibodies are proteins that help the body recognize and fight bacteria and viruses. In people with HID, these antibodies are missing, present in low amounts, or do not work properly.
Because antibodies play a key role in protecting against infection, people with HID often experience frequent, severe, or hard-to-treat infections. These infections most commonly affect the sinuses, ears, and lungs, and can lead to chronic inflammation, tissue damage, and long-term lung disease. Some individuals may also develop gastrointestinal infections, autoimmune conditions, malignancy, or ongoing fatigue.
Humoral immunodeficiencies can vary widely in severity. Some people have mild symptoms that appear later in life, while others develop infections in infancy or childhood. Many forms of HID are treatable with therapies such as immunoglobulin (antibody) replacement, antibiotics, and careful medical monitoring, which can greatly reduce infections and improve quality of life.
HID includes several related conditions and are linked to genetic changes in many different genes. HID affects one or more of the five major classes of antibodies, leading to varied clinical presentations.
Examples include:
- Agammaglobulinemia, in which individuals have profoundly low or absent levels across all antibody classes.
- Common variable immunodeficiency (CVID), a heterogeneous group of disorders defined by low immunoglobulin levels (hypogammaglobulinemia).
- Hyper IgM syndromes, characterized by decreased immunoglobulin G (IgG) levels alongside normal or elevated immunoglobulin M (IgM).
- Single-class antibody deficiencies, where only one antibody type is affected. These include selective IgA deficiency, IgG subclass deficiencies, and specific antibody deficiency.
Together, these conditions highlight the essential role of antibodies in immune defense and the diverse genetic mechanisms that can disrupt their production. HID as a group are a part of a larger grouping of diseases called primary immunodeficiencies (PID), or more recently, inborn errors of immunity (IEI).