Diagnosis: Vasculitic neuropathy
• This figure depicts vasculitic neuropathy. The most commonly involved nerves include peroneal, posterior tibial, and ulnar nerves.
• Involved vessels show characteristic pathologic features in common: inflammation and structural damage to blood vessels walls, leading to ischemic, hemorrhagic, and thrombotic damage to the nerves supplied by those vessels.
• Vasculitis/vasculitides can be classified into two groups: one group results from direct bacterial, fungal, rickettsial, or viral infection, and the other results from immunologic mechanism. For the most immune-mediated vasculitic syndromes, the inciting events that trigger the vasculitis and the precise pathogenic mechanism of vascular damage are not well understood.
• Immune-mediated vasculitic neuropathy can be the primary disease process as in polyarteritis nodosa or Wegener granulomatosis, or can be associated with some other connective tissue disorder, such as rheumatoid arthritis or systemic lupus erythematosus.
• A tissue diagnosis is absolutely essential for the management of patients with suspected vasculitis. Active lesions are characterized by transmural inflammation with concurrent necrosis. Endothelial cell necrosis with hemorrhage may also occur. Mononuclear cells infiltrating the vessels are predominantly T cells and macrophages.
• Vasculitic neuropathy is predominantly axonopathy, and nerve biopsy usually demonstrates varying degrees of nerve fiber loss, with undergoing wallerian degeneration depending on the age of the lesion. Unmyelinated fibers are more resistant to ischemic insults than larger myelinated fibers.
