title: Immunostaining of skin biopsy adds no diagnostic value in MGUS-associated peripheral neuropathy.
abstract: OBJECTIVE
  For several decades an association between MGUS, IgM-MGUS in particular, and peripheral neuropathy has been suspected. Several histopathology studies have shown binding of IgM to myelin and a secondary widening of myelin lamellae in cutaneous nerves and in the sural nerve of patients with IgM-MGUS, or Waldenström's Macroglobulinaemia (WM), and peripheral neuropathy. In this retrospective study we investigated the value of skin biopsy examination in the diagnosis of MGUS- and WM-associated peripheral neuropathy.
  
  
  METHODS
  A total of 117 patients, who were examined for an M-component in serum with associated nerve symptoms, had a skin biopsy taken and examined for immunoglobulin deposition in cutaneous nerves. Thirty-five patients were diagnosed with MGUS or WM and peripheral neuropathy with no other cause of neuropathy. Nineteen patients had MGUS but no peripheral neuropathy.
  
  
  RESULTS
  Of the 35 patients with MGUS or WM and peripheral neuropathy, four had immunoglobulin deposition in the skin biopsy, all of whom had an IgM gammopathy. In the control group of 19 without peripheral neuropathy, three had immunoglobulin deposition in the skin biopsy, all of whom had IgM-MGUS. In both groups, there was a trend towards higher IgM blood levels in patients with immunoglobulin deposition. Half of the patients with IgM gammopathy in the neuropathy group had anti-MAG reactivity, whereas only one in the control group had weak anti-MAG reactivity.
  
  
  CONCLUSIONS
  Our study indicates that examination of skin biopsies for immunoglobulin deposition does not add significant diagnostic value in the evaluation of neuropathies suspected to be caused by MGUS or WM. IgM immunoglobulin deposition in skin biopsy might merely be an epiphenomenon secondary to high IgM blood levels.
authors.affiliation: Department of Neurology, Odense University Hospital, Odense, Denmark. Electronic address: al_zuhairy@hotmail.com.
authors.forename: Ali
authors.initials: A
authors.lastname: Al-Zuhairy
authors.affiliation: Department of Clinical Pathology, Odense University Hospital, Odense, Denmark.
authors.forename: Henrik Daa
authors.initials: HD
authors.lastname: Schrøder
authors.affiliation: Department of Hematology, Vejle Hospital, Vejle, Denmark.
authors.forename: Torben
authors.initials: T
authors.lastname: Plesner
authors.affiliation: Department of Hematology, Odense University Hospital, Odense, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Abildgaard
authors.affiliation: Department of Neurology, Odense University Hospital, Odense, Denmark.
authors.forename: Søren H
authors.initials: SH
authors.lastname: Sindrup
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D005260:Female; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D008998:Monoclonal Gammopathy of Undetermined Significance / Q000150:complications* / Q000175:diagnosis / Q000473:pathology; D010523:Peripheral Nervous System Diseases / Q000209:etiology* / Q000473:pathology; D012189:Retrospective Studies; D012867:Skin / Q000473:pathology*; D008258:Waldenstrom Macroglobulinemia / Q000150:complications* / Q000175:diagnosis / Q000473:pathology
chemical_list: D007075:Immunoglobulin M
keywords: Anti-MAG; Immunoglobulin deposition; MGUS; Peripheral neuropathy; Polyneuropathy; Skin biopsy