To differentiate between vasculitic neuropathies and demyelinating neuropathies. 

Our patient presented with five days of ascending symmetric weakness following a prodromal illness. On further history, he also had four weeks of sharp pains in his upper extremities. Exam was significant for weakness in bilateral ankle dorsiflexion and plantarflexion with preserved reflexes. NCS/EMG was consistent with multiple patchy areas of conduction block and he was diagnosed with an atypical variant of Guillain Barre Syndrome. He completed a course of IVIG without improvement.

Repeat NCS/EMG was completed which showed a multifocal neuropathy with axonal features. C-ANCA returned markedly positive. Peroneal nerve biopsy and peroneus brevis muscle biopsy showed vasculitic changes. He was treated with high dose steroids and rituximab.

Nonsystemic vasculitidies are a rare but potentially treatable cause of neuropathy. Our patient was initially misdiagnosed with Guillain Barre Syndrome and was treated with IVIG. However, the atypical presentation prompted further workup. His initial NCS/EMG actually showed pseudo-conduction block, which can be seen with early nerve infarction. Without a strong clinical suspicion, vasculitic neuropathies can be easily missed.