11. Ethical considerations Tacrolimus and IVIG can have side effects. The known tacrolimus side effects are more severe and more frequent than those of IVIG. It must be noted, however, that the known tacrolimus side effects were assessed in organ transplant patients who had severe medical diseases and were usually treated with more than one immunosuppressant. In patients with autoimmune disorders treated with tacrolimus-monotherapy, the side effects were considerably lower. RE itself is a disease with a deleterious natural course so that the possible risks of an immunotherapy are clearly outweighed. It must be assumed that most RE patients worldwide are treated with any kind of immunotherapy in the early disease stage due to the favorable case reports in the literature. Therefore, a placebo control group appears ethically unacceptable. This is why we chose to compare the two most promising substances. The ethics committee of the University of Bonn has approved the study design.