The commonest primary immunodeficiency is
High-Yield Explanation
Isolated IgA deficiency Extremely low levels of serum & secretory IgA (may be IgG2 & IgG4 too) Defective differentiation of B cells to IgA producing plasma cells CF Mucosal immunity affected Recurrent sinopulmonary infections & diarrhoea When transfused with blood containing IgA may develop fatal anaphylactic reactions