AQP4 and edema: Three children (2.4%) died during follow-up; one patient during acute presentation of ADEM from acute fulminant inflammation inducing cerebral oedema, one with AQP4-Ab NMOSD 10 years after initial presentation during relapse following a hyperkalaemic cardiac arrest, and the patient with primary haemophagocytic lymphohistiocytosis died after an unsuccessful bone marrow transplant with further CNS relapses.