Epidemiology

MNM is a relatively uncommon clinical syndrome. Overall incidence and prevalence rates for MNM are not known. Vasculitic neuropathies (the most common etiology for MNM) occur most frequently in older people, although they may present at any age. The mean age of onset for vasculitic neuropathy ranges from 51-67 years.[3][4][5][6]​​[7]

MNM has been reported to be associated with several conditions.

  • MNM was reported in 65% of patients with nonsystemic vasculitic neuropathy, the most common type of vasculitis affecting the peripheral nerves.[8][9][10]

  • Polyarteritis nodosa targets peripheral nerves more often than other organ systems. Up to 85% of patients with polyarteritis nodosa demonstrate vasculitic neuropathy.[7][11]​​

  • Peripheral neuropathy develops in around 50% to 70% patients with eosinophilic granulomatosis with polyangiitis (formerly known as Churg-Strauss syndrome) or microscopic polyarteritis.[7][12]

  • MNM was reported in about 15% to 20% of patients with granulomatosis with polyangiitis (formerly known as Wegener granulomatosis).[7][13]

  • MNM was reported in approximately 8% of untreated patients referred for treatment of hepatitis C (but this is probably an overestimate).[11] ​Up to 65% of patients with hepatitis C-related cryoglobulinemic vasculitis develop clinically significant neuropathy.[7]

  • MNM is present in 30% to 50% of patients with rheumatoid vasculitis, which affects 5% to 20% of patients with rheumatoid arthritis.[7][14][15][16] Rheumatoid vasculitis usually occurs late in the course of seropositive rheumatoid arthritis, and its incidence has declined in recent past with effective disease-modifying therapies.

  • ​Approximately 8% to 13% of patients with Sjogren syndrome have MNM.[7][17]

  • Around 1% of patients with systemic lupus erythematosus have vasculitis, and 9% of those with vasculitis have evidence of vasculitic neuropathy.[7][18]

  • Approximately 17% of patients with neurosarcoidosis have neuropathy, but <1% of all patients with sarcoidosis develop vasculitic neuropathy.[19]

  • A very small proportion of patients with giant cell arteritis and Henoch-Schonlein purpura have MNM.​[20][21][22]​ Vasculitic neuropathy does not occur in large-vessel arteritis (Takayasu arteritis).

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