You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is The commonest Primary immunodeficiency is ? and explain in detail?
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).