8.28 SFGH morning report pearls: GPA versus MPA, and a bit on metal neuropathy

Granulomatosis with polyangiitis (GPA) versus microscopic polyangiitis (MPA)

ENT findings (sinusitis, otitis media, oral ulcers 90% 35%
pulmonary disease (nodules/patchy/diffuse opacities) common common
Renal disease common common
Cutaneous findings (purpura, ulceration, urticaria) ~50% ~50%
constitutional symptoms (fever, weight loss, anorexia) common common
  • GPA primarily PR3-ANCA
  • MPA primarily MPO-ANCA
  • 20% with GPA and MPA have the alternative ANCA, and 10% are ANCA negative
  • Metal neuropathy:
    • oftentimes distal symmetric sensorimotor polyneuropathy
    • common causes include chronic arsenic intoxication (mining, pesticides, some homeopathic remedies/herbals), mercury (fish polluted with mercury, dentists), gold (s/p treatment with gold therapy), thallium (rodenticide, banned in US), lead (occupational exposure, lead paint, folk remedies)

Hagen et al.  Diagnostic value of standardized assays for anti-neutrophil cytoplasmic antibodies in idiopathic systemic vasculitis.  EC/BCR Project for ANCA Assay Standardization.  Kidney Int. 1988 Mar; 53(3): 743-53.


Falk RJ, King TE.  Clinical manifetations and diagnosis of granulomatosis with polyangiitis and microscopic polyangiitis.  UptoDate.  2014, Jan.  


Pratt RW and Weimer LH.  Medication and toxin-induced peripheral neuropathy.  Semin Neurol 2005 Jun; 25(2): 204-16.



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