Selective deficiency of IgG and IgA as a first stage defect in B cell differentiation

A case of selective deficiency of IgG and IgA, in a 13-year old girl, is described. Immunologic investigations, showing an almost complete absence of IgG- and IgA-bearing lymphocytes and significant amounts of IgD and IgM positive cells, suggest the possibility of a block in the shift from IgM to IgG synthesis at the B lymphocyte level.