Illustrative cases on individualizing immunoglobulin therapy in primary immunodeficiency disease

To illustrate the need for individualized immunoglobulin therapy in patients with primary immunodeficiency diseases (PIDDs) and review current evidence on how best to identify the biological serum IgG level in patients with antibody-deficient PIDD.

Two case studies from the author's clinical practice are discussed. PubMed and Ovid MEDLINE databases were searched for articles pertaining to serum immunoglobulin levels in patients with PIDD and the relation of trough IgG levels to infection incidence and outcomes.

Articles and case studies were selected for their relevance to the individualization of IgG therapy for patients with PIDD. The case studies support the position that each patient has a specific "biological" serum IgG level associated with decreasing or preventing recurrent infection.

Patients with antibody-deficient PIDD are routinely treated with lifelong immunoglobulin replacement. Although a starting dose has been suggested, the dose of IgG that maintains serum IgG levels that protect against severe or recurrent infection has not been determined. It is likely the serum IgG level required to prevent infection in these patients varies as it does in normal individuals. This biological serum IgG level must be identified for each patient by plotting documented infections vs serum IgG levels over time.

Clinical experience and recent evidence suggest that optimal treatment of patients with PIDD involves individualizing IgG treatment to identify the optimal IgG serum levels that are required for each patient to become free of recurrent infection or pneumonia instead of trying to achieve a single optimal serum IgG level for all patients.