IgG subclass deficiencies: identifying and treating patients at risk.

IgG subclass deficiencies can increase the risk of pulmonary infections or other severe recurrent infections. Various groups of patients were studied in an attempt to learn more about (1) measuring the IgG subclass levels (particularly IgG4 levels) of possible high-risk patients; (2) identifying those patients who are at risk of developing recurrent infections, and (3) treating these patients once they have been identified. Individual cases are presented, and associations of isolated subclass deficiencies are examined with respect to infection. Replacement therapy with plasma or intravenous immunoglobulin (IVIG) to increase titers of deficient or absent subclasses is suggested.