Interestingly, a recent study reported a loss of aquaporin-4 (AQP4) and other astrocytic proteins in BCS, which in some lesions preceded the loss of myelin, suggesting that BCS might, at least in a subset of cases, be primarily an astrocytopathy, just as AQP4-IgG-positive NMO [31]. The gene discussed is AQP4; the disease is neuromyelitis optica.