The commonest primary immunodeficiency is (AIPG 2010)
|A||Common variable immunodeficiency|
|B||Isolated IgA immunodeficiency|
"Selective deficiency of IgA is the most common immunodeficiency, occurring in about 1 in 1000 individuals".
a. Chandrasoma Taylor
i. "An inability to produce antibodies up the IgA1 and IgA2 subclasses occurs in approximately 1 in 600 individuals, a much higher incidence than is seen for other primary immunodeficiency". - Harrison
b. IgA deficiency
i. IgA deficiency is often familial
ii. It may be acquired by :
• Congenital infections such as toxoplasmosis, rubella, CMV
• Treatment with phenytoin
i. Block in B cell differentiation due to defective interaction between T and B cells. Naive B cells are not able to differentiate into IgA - producing cells.
d. Features →
i. Respiratory infections
ii. Chronic diarrheal diseases
iii. Increased incidence of asthma and other atopic disease
iv. Frequent production of autoantibodies
v. Association with arthritis and SLE
vi. Reduction of IgG2 and IgG4
e. Common variable immunodeficiency
The feature common to all patients is hypogammaglobulinemia generally affecting all the antibody classes but sometimes only IgG.
f. Pathogenesis →
i. Patients have normal numbers of B cells.
ii. B cells are not able to differentiate into plasma cells.
g. Features →
i. Recurrent sinopulmonary infections
ii. Recurrent herpesvirus infection
iii. Persistent diarrhea caused by G. lamblia
iv. Meningoencephalitis caused by enterovirus.
v. High incidence of autoimmune diseases e.g. R.
vi. Increased risk of lymphoid malignancy and gastric cancer, particularly in women.
vii. Relatives of these patients have high incidence of selective IgA deficiency.
viii. T/t → I. V. immunoglobulin
Note: AIDS is a type of secondary immunodeficiency (not primary).