Polyarteritis nodosa (PAN) is a systemic necrotizing inflammation of blood vessels (vasculitis) affecting medium-sized muscular arteries, typically involving the arteries of the kidneys and other internal organs but generally sparing the lungs' circulation.

[6] These manifestations result from ischemic damage to affected organs, often the skin, heart, kidneys, and nervous system.

[6] Neurologic system: Nerve involvement may cause sensory changes with numbness, pain, burning, and weakness (peripheral neuropathy).

[6] Mononeuritis multiplex develops in more than 70% of patients with polyarteritis nodosa because of damage to arteries supplying large peripheral nerves.

Most cases are marked by asymmetric polyneuropathy, but progressive disease can lead to symmetric nerve involvement.

Diagnosis is generally based on the physical examination and a few laboratory studies that help confirm the diagnosis:[citation needed] A patient is said to have polyarteritis nodosa if he or she has three of the 10 signs known as the 1990 American College of Rheumatology (ACR)[11] criteria, when a radiographic or pathological diagnosis of vasculitis is made: In polyarteritis nodosa, small aneurysms are strung like the beads of a rosary,[4] therefore making this "rosary sign" an important diagnostic feature of the vasculitis.

Subsequent studies did not confirm their diagnostic utility, demonstrating a significant dependence of their discriminative abilities on the prevalence of the various vasculitides in the analyzed populations.

Recently, an original study, combining the analysis of more than 100 items used to describe patients' characteristics in a large sample of vasculitides with a computer simulation technique designed to test the potential diagnostic utility of the various criteria, proposed a set of eight positively or negatively discriminating items to be used as a screening tool for diagnosis in patients suspected of systemic vasculitis.

[14] Some patients have entered a remission phase when a four-dose infusion of rituximab is used before the leflunomide treatment is begun.

[6] In the 1956 American film Bigger Than Life, the protagonist character played by James Mason is diagnosed with polyarteritis nodosa after experiencing excruciating chest pain and is treated with cortisone.