Neuro-Muscular Disease and the Immune System

The interneuron plays an integral role in the dance between agonist and antagonist muscles, alternating contraction and relaxation of skeletal muscles for smooth motor functions. In stiff-person syndrome, an autoimmune process disrupts the proper functioning of the spinal interneurons, resulting in co- contraction of agonist and antagonist muscles. Patients may have raised anti-glutamic acid decarboxylase (GAD) or anti-amphiphysin antibodies, the former associated with thymoma; the latter a marker of more general paraneoplastic phenomena.