Some patients develop NMO years after they have been diagnosed with myastenia gravis (MG). This is a very interesting coincidence, since NMO is a disease of the CNS, while MG is an autoimmune disease of the PNS affecting the neuromuscular end plate. However, in some circumstances, also muscles of patients with NMO or of experimental NMO models are targeted by antibodies and T cells. We currently analyze whether muscle inflammation leads to the liberation and/or better presentation of proteins which may serve as additional targets for the immune system, and whether this mechanism causes the ?switch? between these two different autoimmune diseases.