Immunotherapy-Responsive Neuropathic Pain and Allodynia in a Patient With Glycine Receptor Autoantibodies: A Case Report

OBJECTIVES: Neuropathic pain is common and distressing. Improved mechanistic understanding and pharmacotherapies are urgently needed. Molecularly specific pain syndromes may provide insights with translational relevance. Glycine receptors are known to play a key role in inhibitory neurotransmission in the spinal dorsal horn and have therefore been considered as targets for analgesic development. While autoantibodies directed against glycine receptors may rarely arise spontaneously in humans, a detailed phenotype of neuropathic pain and allodynia in association with these autoantibodies has not been described. METHODS: We describe the case of a previously well adult presenting with severe neuropathic pain and allodynia as part of an autoimmune brainstem and spinal syndrome with glycine receptor autoantibodies. RESULTS: Our patient experienced a severe illness, including marked neuropathic pain and allodynia, hypoventilation, tetraparesis, and ophthalmoplegia. A diagnosis of progressive encephalomyelitis with rigidity and myoclonus was made. Neuropathic pain was characterized with validated instruments and responded promptly to cause-directed immunotherapy. DISCUSSION: A detailed longitudinal phenotyping, using validated pain measurement instruments, of severe neuropathic pain and allodynia associated with likely pathogenic glycine receptor autoantibodies is reported. This case may have relevance for translational development of analgesics targeting glycinergic neurotransmission.