title: Distinctive pathologic findings in proximal diabetic neuropathy (diabetic amyotrophy).
abstract: OBJECTIVE
  To investigate the pathogenesis of proximal diabetic neuropathy (PDN) with nerve and muscle biopsies.
  
  
  BACKGROUND
  Recent evidence suggests that nerve ischemia secondary to immune-mediated vasculopathy rather than diabetic microangiopathy may be responsible for PDN.
  
  
  METHODS
  - Fifteen patients with PDN and two diabetic controls underwent nerve and muscle biopsy and clinical, electrophysiologic, and laboratory evaluation. There were eight men and seven women between 49 and 79 years of age with type II diabetes. All had progressive, painful, asymmetric, proximal weakness with duration of 5 weeks to 12 months. None had evidence of systemic autoimmune disorder.
  
  
  RESULTS
  Four patients showed the distinctive findings of polymorphonuclear small-vessel vasculitis affecting epineurial vessels with transmural infiltration of postcapillary venules with polymorphonuclear leukocytes. Immunoglobulin M (IgM) deposits were found along the endothelium and intramurally in affected vessels. IgM staining was seen in the subperineurial space and in the endoneurium. Activated complement deposition was seen along endothelium of small vessels. Three of these four patients were evaluated within 6 seeks of onset of PDN, and the fourth patient during acute flare of PDN 6 months after the initial onset. Six patients showed "perivasculitis" with mononuclear cell infiltrates around small epineurial vessels without vasculitis (fibrinoid necrosis or transmural inflammation). One patient showed recanalized vessels with transmural lymphocytes without fibrinoid necrosis, possibly suggesting healed vasculitis.
  
  
  CONCLUSIONS
  These distinctive pathologic findings support that proximal diabetic neuropathy has an immune-mediated inflammatory basis and suggest that polymorphonuclear vasculitis with immune complex and complement deposition may be the primary event in the acute phase of proximal diabetic neuropathy.
authors.affiliation: Department of Neurology, University of Minnesota, Minneapolis 55455, USA. pkelkar@tc.umn.edu
authors.forename: P
authors.initials: P
authors.lastname: Kelkar
authors.forename: M
authors.initials: M
authors.lastname: Masood
authors.forename: G J
authors.initials: GJ
authors.lastname: Parry
mesh_terms: D000368:Aged; D003929:Diabetic Neuropathies / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000473:pathology; D009412:Nerve Fibers / Q000473:pathology*