Polyarteritis Nodosa (PAN)
(Polyarteritis; Periarteritis Nodosa)
(See also Overview of Vasculitis.)
Polyarteritis nodosa is a form of vasculitis involving inflammation of medium sized arteries.
Any organ can be affected, but usually not the lungs.
Polyarteritis nodosa can be rapidly fatal or develop gradually.
Symptoms vary depending on which organ is affected.
Biopsy of an affected artery can confirm the diagnosis.
Prompt treatment with a corticosteroid, another drug that suppresses the immune system, or both can delay or prevent death.
Polyarteritis nodosa most often develops during middle age, usually when people are in their 50s, but it can occur at any age. It is rare.
The cause is unknown, but it sometimes appears to be triggered by certain viral infections (such as hepatitis B or in rare cases hepatitis C) or drugs. About 20% of people with polyarteritis nodosa have hepatitis B or C. Drugs may cause the disorder, but most often no trigger can be identified.
The kidneys, skin, nerves, joints, muscles, and digestive tract are most commonly affected. The liver and heart are often affected as well.
The disorder can be mild at first but can worsen rapidly and be fatal within several months, or it can develop gradually as a chronic debilitating disease. Any organ or combination of organs can be affected. However, usually the lungs are not affected. Symptoms depend on which organs are affected and how severely they are affected. Occasionally, only one organ (such as the intestine) or a nerve is affected. People may have general symptoms at first. They may feel generally ill and tired and have a fever. They may lose their appetite and lose weight. Night sweats and generalized weakness are common symptoms.
Other symptoms occur when the arteries that carry blood to an organ are damaged, and the organ does not receive enough blood to function normally. Thus, symptoms vary depending on the organ that is affected:
Joints: Muscle pain, tenderness, and weakness; and joint pain (common) and joint inflammation (arthritis)
Digestive tract: Severe pain, bloody diarrhea, nausea, vomiting, and tears (perforations) in the intestine
Heart: Chest pain (angina), heart attacks, and heart failure (see Overview of Coronary Artery Disease (CAD))
Brain: Headaches, seizures, and strokes
Nerves: Patchy numbness, tingling, weakness, or paralysis in a hand or foot
Liver: Liver damage
Skin: Blue or red discoloration of the fingers or toes and occasionally skin sores
Genitals: Pain and tenderness of the testicles and inflammation in the testes (orchitis)
Sometimes damage to an organ is irreversible, and some or all of the organ function is lost. A weakened artery may rupture, causing internal bleeding. Problems, such as a heart attack, can occur long after the inflammation has been treated.
Polyarteritis nodosa can be difficult to diagnose. Doctors suspect polyarteritis nodosa when people have a certain combination of symptoms and blood test results. For example, doctors may suspect the diagnosis if a previously healthy middle-aged person has various combinations of symptoms such as an unexplained fever, evidence of a certain pattern of nerve damage (such as difficulty raising a foot or bending the wrist), sores on the skin, pain in the abdomen or limbs, joint or muscle pain, or rapidly developing high blood pressure.
To confirm the diagnosis, doctors may take a small sample of an affected organ and examine it under a microscope (biopsy). Doctors may do electromyography and nerve conduction studies to help select the area for a muscle or nerve biopsy. Arteriography (angiography of arteries) or sometimes magnetic resonance angiography may be done to check for irregularities such as narrowing and dilations (aneurysms) in the wall of affected arteries. For arteriography, images are recorded after a dye that is visible on x-rays (radiopaque contrast agent) is injected. Magnetic resonance angiography is less likely to confirm the diagnosis than angiography.
Treatment is aimed at preventing damage from developing but often cannot reverse damage that has already occurred. Treatment depends on the severity of the disorder. Any drugs that may have triggered the disorder are stopped.
High doses of a corticosteroid, such as prednisone, can prevent polyarteritis nodosa from worsening and help people feel better. The goal is a symptom-free period (remission). Because many people need long-term treatment with a corticosteroid and because long-term treatment can have significant side effects, doctors reduce the dose once symptoms have subsided.
If the corticosteroid does not reduce the inflammation adequately, drugs that suppress the immune system (immunosuppressants), such as cyclophosphamide, may be given with the corticosteroid. Taking a corticosteroid or another immunosuppressant for a long time reduces the body’s ability to fight infections. Thus, people so treated have an increased risk of infections, which may be serious or fatal if not recognized and treated promptly.
Other treatments, such as those used to control high blood pressure, are often needed to prevent damage to internal organs. Hepatitis B and C, if present, are treated with antiviral drugs after the inflammation has been controlled.