What is specific antibody deficiency?
A patient with a specific antibody deficiency cannot produce immunoglobulin G (IgG) molecules to the polysaccharides in encapsulated bacteria (such as Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae). This makes the patient vulnerable to recurrent bacterial lung infections (pneumonia), sinus infections, ear infections (otitis media), and others.
Specific antibody deficiency is also called selective antibody deficiency, partial antibody deficiency, and impaired polysaccharide responsiveness.
Who gets specific antibody deficiency?
Specific antibody deficiency is usually diagnosed in preschool children and occurs in both girls and boys of all races.
What causes specific antibody deficiency?
The exact cause of specific antibody deficiency is not known but it is likely due to a genetic mutation. It may be due to a breakdown in communication between B lymphocytes and other cells in the immune system.
What are the signs and symptoms of specific antibody deficiency?
Some patients with specific antibody deficiency are asymptomatic because other components of their immune system are still functional. Other patients may present with:
- Otitis media, sinusitis, bronchitis, pneumonia, and other bacterial infections
- Infections that are not as severe as those with severe combined immunodeficiency or x-related agammaglobulinaemia
- Atopic eczema and asthma (these affect 50% of patients with specific antibody deficiency).
How is specific antibody deficiency diagnosed?
The diagnosis of specific antibody deficiency is based on:
- Normal levels of T and B lymphocytes
- Normal levels of immunoglobulins, including IgG subclasses
- Absence of another detectable immunodeficiency disease (including human immunodeficiency virus infection [HIV])
- History of recurrent respiratory infections
- Administering the standard pneumococcal vaccine then finding a lack of antibody formation after 4–6 weeks.
How is specific antibody deficiency treated?
Treatment for specific antibody deficiency centres on:
- Infection control with antibiotics at a high dosage for 10 days or daily for prophylaxis against infection
- Immunoglobulin replacement therapy administered intravenously or subcutaneously if indicated
- Stimulating a better immune response to vaccination by using a heptavalent or 13-valent pneumococcal polysaccharide vaccine conjugated with protein and Haemophilus influenzae type B (Hib) vaccine.
The primary goals of treatment are to prevent bronchiectasis and scarring in the lungs from repeated respiratory infections and to maintain the overall quality of life.
What is the prognosis for specific antibody deficiency?
The prognosis for patients with specific antibody deficiency is generally reasonable. Children have been known to outgrow specific antibody deficiency naturally and those who do not are still able to maintain a good quality of life with antibiotic and immunoglobulin therapy.