Polyarteritis nodosa (PAN) is a systemic illness that most often involves the skin, kidneys, and gastrointestinal tract, in addition to the peripheral nervous system. It most often affects middle-aged individuals, men more than women. The particular type of peripheral neuropathy is often mononeuropathy or mononeuritis multiplex—a condition in which there is discrete involvement of multiple individual nerves. Definitive diagnosis of the vascular nature of the neuropathy requires peripheral nerve biopsy, which will demonstrate inflammation throughout the walls of small and medium-sized arteries. The CNS is also frequently involved in PAN. Constitutional symptoms, including fever, fatigue, and diffuse muscle and joint pain, are common and raise the suspicion of a systemic illness. Treatment generally involves the use of corticosteroids and immunosuppressive agents such as cyclophosphamide or azathioprine.