Perineuritis in acute lyme neuroborreliosis.

Perineuritis is an unusual cause of direct peripheral nerve injury. We describe the clinicopathologic features of a 56-year-old man with mononeuritis multiplex due to Lyme disease; sural nerve biopsy demonstrated florid perineuritis. Treatment with intravenous ceftriaxone resulted in marked neurologic improvement. This study supports the notion that perineuritis forms part of the pathogenesis in acute Lyme neuroborreliosis.