Movement disorders with autoimmune neuromuscular origin: an overview of Isaacs' syndrome, stiff person syndrome, immune-mediated rippling muscle disease.

Movement disorders associated with neuromuscular diseases are often underrecognized, yet they represent a distinct clinical entity. Abnormalities in areas of the peripheral nervous system, i.e., nerves and muscles, can stem from dysfunction of ion channels and proteins involved in membrane excitability. Hyperexcitability of peripheral motor nerves presents as cramps, stiffness, abnormal posture and gait, as well as changes in motor unit potentials during electromyography studies; hence, it may be classified as a movement problem. Etiologies range from hereditary, immune-mediated, or may be secondary to structural changes. This review focuses on peripheral nervous system and muscle-derived movement disorders associated with autoantibodies. It aims to highlight immune-mediated peripheral nerve hyperexcitability syndromes, stiff-person spectrum disorders, and immune-mediated rippling muscle disease (a movement disorder of muscular origin). It also discusses pathophysiology, diagnosis (particularly immunologic markers), and therapeutics.