Our observations may have clinical implication as the potential importance of the ectopic GC in disease pathophysiologies imply that therapies that inhibit the formation and functioning of ectopic GC may be efficacious, such as blockade of IL-21 signaling by monoclonal antibodies or IL-21 receptor antagonists; especially both patients had severe myelitis and/or ON, and the second patient did not respond to rituximab. Here, IL21R is linked to myelitis.