Case reports of evaluation and desensitization for anti-thymocyte globulin hypersensitivity.

Background: Biologic products of heterologous sera have been used to treat a variety of conditions. One example is anti-thymocyte globulin (ATG), which is approved for use in the management of renal transplantation and for aplastic anemia. As ATG is a product of heterologous sera it has the potential for adverse reactions, including anaphylaxis. Patients can be skin tested prior to ATG administration to aid in determining hypersensitivity status to ATG.

Objective: To provide case reports to illustrate evaluation for ATG hypersensitivity. Also, to discuss desensitization procedures for patients who are found to have ATG hypersensitivity, and yet are to receive the medication as it is judged to be essential.

Case Reports: We report four patients who were to receive ATG. The results of skin testing and each patient's response to ATG are reviewed to illustrate problems that can occur in evaluating the hypersensitivity status of these patients. Further, some patients also underwent ATG desensitization, but none completed the entire protocol successfully. Their outcomes are reviewed to illustrate problems that can occur with the desensitization procedure.

Conclusion: Anti-thymocyte globulin is a product of heterologous sera and has the potential to produce anaphylaxis. It is recommended that patients be skin tested prior to administration to aid in determining hypersensitivity status. Those patients who demonstrate hypersensitivity to ATG should not receive ATG unless it is deemed essential and benefits are judged to outweigh risks. In these circumstances, patients are candidates for ATG desensitization. Complications with desensitization occurred in the cases attempted, and highlights that desensitization to ATG, a xenogeneic protein, carries risk and can be difficult. Physicians involved in such cases should be familiar with interpretation of skin tests and problems that can occur with desensitization.