Though AQP4 is expressed in some peripheral organs outside of the central nervous system, including skeletal muscle, kidney and stomach [8, 19], these organs are rarely affected in NMO, with only a few reports of NMO-associated myositis associated with elevated creatine phosphokinase and skeletal muscle pathology [7, 13, 27]. Here, AQP4 is linked to neuromyelitis optica.