The commonest Primary immunodeficiency is ?

Ans. is 'b' i.e., Isolated IgA immunodeficiency "Selective deficiency of IgA is the most common immunodeficiency, occuring in about 1 in 1000 individuals". - Chandrasoma Taylor "An inability to produce antibodies up the IgA 1 and IgA2 subclasses occurs in approximately I in 600 individuals, a much higher incidence than is seen for other primary immunodeficiency". - Harrison IgA deficiency . IgA deficiency is often familial . It may be acquired by : - Congenital infections such as toxoplasmosis, rubella, CMV - Treatment with phenytoin Pathogenesis --> . 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. Features --> . Respiratory infections . Chronic diarrheal diseases . Increased incidence of asthma and other atopic disease . Frequent production of autoantibodies . Association with ahritis and SLE . Reduction of IgG2 and IgG4 Treatment - . Symptomatic . No benefit of immunoglobulin (IgA) infusion because of increased risk of development of autoantibodies against IgA. . Exceptionally immunoglobulin infusion may help in patients with IgG2 and IgG4 deficiency. Common variable immunodeficiency . The feature common to all patients is hypogammaglobulinemia generally affecting all the antibody classes but sometimes only IgG. . Pathogenesis ---> . Patients have normal numbers of B cells. . B cells are not able to differentiate into plasma cells. . Features - . Recurrent sinopulmonary infections . Recurrent herpesvirus infection . Persistant diarrhea caused by G lambia . Meningoencephalitis caused by enterovirus. . High incidence of autoimmune diseases eg. R.A. . Increased risk of lymphoid malignancy and gastric cancer, paicularly in women. . Relatives of these patients have high incidence of selective IgA deficiency. . T/t I.V. immunoglobulin Note : AIDS is a type of secondary immunodeficiency (not primary).