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Abstract
Objective: Autoantibodies targeting voltage-gated potassium channel (VGKC) complexes cause a spectrum of neuronal hyperexcitability disorders. We investigated pain as a manifestation of VGKC-complex autoimmunity.
Methods: We reviewed the prevalence and characteristics of pain in VGKC-complex-immunoglobulin G (IgG)–seropositive patients in 25 months of comprehensive service testing for neural autoantibodies, subtyped positive sera for LGI1-IgG and CASPR2-IgG specificities, and reviewed pain prevalence in autoimmune control patients.
Results: VGKC-complex-IgG was identified in 1,992 patients of 54,853 tested (4%). Of 316 evaluated neurologically at Mayo Clinic, 159 (50%) had pain, in isolation (28%) or with accompanying neurologic manifestations (72%), and not attributable to alternative cause. Pain was subacute in onset, chronic in course, neuropathic, nociceptive, regional, or diffuse and sometimes attributed to fibromyalgia (6%) or psychogenic cause (13%). Most patients had normal peripheral nervous system function, measured by neuropathy impairment scores and nerve conduction. Evidence of neuronal hyperexcitability (hyperhidrosis, quantitative heat-pain hyperalgesia, or electromyographic excitability) was 25-fold more common in pain patients. Pain management required multiple medications in 70% (narcotics, 30%); 13 of 16 patients reported pain relief with immunotherapy. Pain was significantly associated with CASPR2-IgG-positivity (16% positive with pain, 7% without pain; p = 0.014) but not with LGI1-IgG. Less than 10% of 167 patients with neural autoantibodies other than VGKC-complex-IgG reported pain.
Conclusions: Chronic idiopathic pain is a syndromic manifestation of VGKC-complex autoimmunity. Hyperexcitability of nociceptive pathways is implicated. CASPR2-IgG significantly associates with pain, but in most patients the antigenic VGKC-complex molecule remains to be determined. VGKC-complex autoimmunity represents an important new direction for pain research and therapy.
GLOSSARY
- IASP=
- International Association for the Study of Pain;
- IgG=
- immunoglobulin G;
- IVIg=
- IV immune globulin;
- NIS=
- Neuropathy Impairment Score;
- VGKC=
- voltage-gated potassium channel
Footnotes
Study funding: Mayo Foundation and a NIH grant (NS065007, C.J.K.) and Mayo Clinic CTSA through grant number UL1 RR024150 from the National Center for Research Resources (NCRR), a component of the NIH.
Editorial, p. 1080
Supplemental data at www.neurology.org
- Received November 28, 2011.
- Accepted March 8, 2012.
- Copyright © 2012 by AAN Enterprises, Inc.
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