What is low Immunoglobulin G (IgG)?

From the Guidelines

Low IgG, also known as hypogammaglobulinemia, is a condition characterized by abnormally low levels of immunoglobulin G (IgG) in the blood, increasing the risk of infections, particularly with encapsulated bacteria, and is associated with decreased overall survival. This condition is defined by low serum IgG levels 1, and it has been observed that treatment with certain therapies, such as bispecific antibody therapy, can lead to prolonged hypogammaglobulinemia, further increasing infection risk 1.

Key Points

• Low IgG levels are associated with increased infection risk and decreased overall survival 1
• Hypogammaglobulinemia can be caused by various factors, including secondary immune deficiencies in patients with multiple myeloma (MM) 1
• The condition can lead to recurrent infections, particularly with encapsulated bacteria, and is a significant concern in patients with compromised immune systems 1

Diagnosis and Treatment

• Diagnosis of low IgG involves blood tests measuring immunoglobulin levels, with IgG levels below a certain threshold considered low 1
• Treatment may involve immunoglobulin replacement therapy, although the specific details of this treatment are not provided in the available evidence 1
• Patients with low IgG should practice good hygiene, avoid crowds during illness outbreaks, and promptly treat infections to minimize the risk of complications [based on general medical knowledge]

From the Research

Definition of Low IgG

Low IgG refers to a condition where the levels of Immunoglobulin G (IgG) in the blood are lower than normal. IgG is a type of antibody that plays a crucial role in the immune system by helping to fight off infections.

Causes of Low IgG

• Primary hypogammaglobulinemia, a condition where the immune system does not produce enough antibodies 2
• Secondary hypogammaglobulinemia, which can be caused by certain medications, infections, or other medical conditions 3
• Immunodeficiency syndromes, which can be inherited or acquired 4

Symptoms of Low IgG

• Recurrent infections, such as sinusitis, pneumonia, and otitis 5
• Autoimmunity, allergies, and neoplasias 5
• Airway manifestations, such as rhinitis and asthma 5

Treatment of Low IgG

• Immunoglobulin replacement therapy, which involves administering IgG intravenously or subcutaneously to increase blood levels 2, 6, 3
• Prophylactic antibiotic therapy to prevent infections 5
• Treatment of underlying conditions that may be contributing to low IgG levels 5

IgG Levels and Infection Risk

• Sustained, very low levels of IgG (<100 mg/dL) are associated with an increased risk of infections 4
• Replenishment of IgG to levels of approximately 500 mg/dL can reduce the infection risk to background 4
• Higher levels of IgG may be necessary in the presence of certain comorbidities 4