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Patient’s Right Leg Before Treatment

This video illustrates muscle twitching (myokymia) in the calf of a 42-year-old man with psoriasis due to Isaacs syndrome, a syndrome of neuromyotonia (peripheral nerve hyperexcitability) that can be genetic, due to autoimmune disease, or be the manifestations of a paraneoplastic syndrome. This patient had voltage-gated potassium channel (VGKC)–complex antibodies against CASPR2 and LGI1, previously described in association with psoriasis, so the etiology was presumed to be autoimmune. The patient responded to mycophenolate mofetil and prednisone.

JN Learning™ from JAMA Network is your new home for CME and MOC from a source you trust. Earn AMA PRA Category 1 CME Credit™ from relevant articles, audio, and Clinical Challenge image quizzes, explore interactives and videos, and – depending on your specialty or state – have your MOC points automatically transferred to the relevant board. Learn more about CME

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