Polyarteritis nodosa is a rare multi-system disorder characterized by widespread inflammation, weakening, and damage to small and medium-sized arteries. Blood vessels in any organ or organ system may be affected, including those supplying the kidneys, heart, intestine, nervous system, and/or skeletal muscles. Damage to affected arteries may result in abnormally increased blood pressure (hypertension), "ballooning" (aneurysm) of an arterial wall, the formation of blood clots (thrombosis), obstruction of blood supply to certain tissues, and/or tissue damage and loss (necrosis) in certain affected areas.
The disorder is more common among men, and is more likely to present during early middle age, between 40 and 50 years.
Although the exact cause of polyarteritis nodosa is not known, it is clear that an attack may be triggered by any of several drugs or vaccines or by a reaction to infections (either bacterial or viral) such as strep or staph infections or hepatitis B virus. Many researchers suspect that the disorder is due to disturbances of the body's immune system. Confirming the diagnosis required either a biopsy showing small or medium sized arteries with alternating areas of stenosis (constriction or block) and dilation.