Polyarteritis nodosa, also known as polyarteritis or periarteritis nodosa, is a necrotizing vasculitis disease that affects medium and small arteries. Polyarteritis nodosa can affect any organ in the human body, but the skin, joints, peripheral nerves, gastrointestinal tract and kidneys are most commonly affected. The severity of the lesions varies greatly between individuals. Polyarteritis nodosa can also be combined with other diseases such as rheumatoid arthritis and Sjögren's syndrome. According to the size of the affected blood vessels, it is divided into classic polyarteritis nodosa and micro polyarteritis. The former invades medium-sized arteries and their branches, and the latter involves small arteries and small veins. It is characterized by necrotizing, non-granulomatous vasculitis of small and medium arteries. This is because vascular damage does not only affect the outer layer of the arterial wall, but may also affect all layers of the arterial wall at the same time, causing necrotizing arteritis, and finally leading to multiple aneurysms, thrombosis or infarction.