title: A subset of fibromyalgia patients have findings suggestive of chronic inflammatory demyelinating polyneuropathy and appear to respond to IVIg.
abstract: OBJECTIVE
  The aetiopathogenesis of the fibromyalgia syndrome (FMS) remains unknown. Recent reports, however, suggest that a subgroup of FMS subjects has an immune-mediated disease. Therefore, our primary objective was to study FMS subjects for evidence of an immune-mediated demyelinating polyneuropathy. Our secondary objective was to determine the effects of treating these FMS subjects with the immune modulator, intravenous immunoglobulin (IVIg).
  
  
  METHODS
  Fifty-eight FMS subjects, 26 rheumatic non-FMS subjects and 52 non-rheumatic non-FMS subjects were studied. Subjective measures of paraesthesias, weakness, stocking hypaesthesia, pain, fatigue and stiffness were made. Objective measures of tenderness, proximal muscle strength and electrodiagnostic (EDX) evidence of polyneuropathy and demyelination were also made. Eleven other FMS subjects underwent sural nerve biopsy.
  
  
  RESULTS
  Paraesthesias, subjective weakness and stocking hypaesthesia were more common in FMS than in rheumatic non-FMS (P < or = 0.0001). Proximal muscle strength was less in FMS than in rheumatic non-FMS (P < or = 0.0001). EDX demonstrated a distal demyelinating polyneuropathy, suggestive of chronic inflammatory demyelinating polyneuropathy (CIDP), in 33% of FMS subjects. No rheumatic non-FMS subject had polyneuropathy (P = 0.005), or demyelination (P = 0.05). Fifteen FMS/CIDP subjects were subsequently treated with IVIg (400 mg/kg each day for 5 days). Pain (P = 0.01), tenderness (P = 0.001) and strength (P = 0.04) improved significantly. Fatigue and stiffness trended towards improvement.
  
  
  CONCLUSIONS
  A significant subset of FMS subjects have clinical and EDX findings suggestive of CIDP. IVIg treatment shows promise in treating this subset. These observations have implications for better understanding and treating some FMS patients.
authors.affiliation: Division of Rheumatology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA. xjcaro@earthlink.net
authors.forename: X J
authors.initials: XJ
authors.lastname: Caro
authors.forename: E F
authors.initials: EF
authors.lastname: Winter
authors.forename: A J
authors.initials: AJ
authors.lastname: Dumas
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005221:Fatigue; D005260:Female; D005356:Fibromyalgia / Q000188:drug therapy* / Q000453:epidemiology* / Q000276:immunology; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use*; D007155:Immunologic Factors / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018908:Muscle Weakness / Q000503:physiopathology; D010146:Pain; D010292:Paresthesia / Q000503:physiopathology; D020277:Polyradiculoneuropathy, Chronic Inflammatory Demyelinating / Q000150:complications* / Q000503:physiopathology; D012216:Rheumatic Diseases / Q000503:physiopathology
chemical_list: D016756:Immunoglobulins, Intravenous; D007155:Immunologic Factors