Autoimmune aquaporin-4 induced damage beyond the central nervous system

Initially, it was believed that Aquaporin-4 (AQP4)- immunoglobulin G (IgG) only affected the central nervous system (CNS), and peripheral AQP4-expressing organs were usually spared. However, in recent years, increasing evidence has demonstrated that AQP4-IgG causes damage to peripheral organs beyond the CNS such as skeletal muscle, vestibulocochlear nerves, gastrointestinal tract, blood system, kidney, lung and placenta. Recently, the term "autoimmune aquaporin-4 channelopathy" has been proposed to incorporate a wide range of diseases associated with AQP4-IgG, including neuromyelitis optica spectrum disorders and AQP4-IgG-induced peripheral nerves system damage. Herein, we provide an overview of the clinical evidence of AQP4-IgG-associated peripheral organ damages and discuss the pathogenesis.