This is supported by findings that link other electrolytes, such as CSF chloride, to disease activity in MS, suggesting a broader impact of neuroinflammation on CSF ion composition.27‐29 The importance of potassium homeostasis is further highlighted by studies on the astroglial potassium channel Kir4.1, against which autoantibodies have been detected in a subset of patients with MS.30 The gene discussed is KCNA3; the disease is myeloid sarcoma.