Definition

Polyarteritis nodosa is a condition characterized by widespread inflammation as well as weakness and damage to small and medium-sized arteries. This inflammation and damage primarily occur at arterial branch points. However, large arteries (such as the aorta and its main branches), very small blood vessels (capillaries and small arterioles), and the venous system are typically unaffected.

Polyarteritis nodosa is more commonly found in men, particularly those in middle age, between 45 and 65 years old, though it can occur at any age. It is estimated to affect 1 in 100,000 people.

Causes

The exact cause of polyarteritis nodosa is unknown. Most sufferers do not have a clear trigger. However, it is believed that the damage to blood vessels may be triggered by:

• Certain medications or vaccines may stimulate an immune reaction, causing polyarteritis nodosa.
• Reactions to bacterial or viral infections, such as those from Streptococcus sp., Staphylococcus sp., and hepatitis B virus. Research indicates that bacterial and viral infections may trigger an abnormal immune response, potentially leading to polyarteritis nodosa. Hepatitis B virus replication can itself cause blood vessel wall damage and trigger immune responses that induce polyarteritis nodosa. This condition can occur at any stage of hepatitis B, whether acute or chronic, but it usually appears within 6 months of infection. Hepatitis B patients are more likely to experience gastrointestinal symptoms, severe hypertension, kidney damage, and inflammation of the testes and epididymis. Before the widespread use of hepatitis B vaccines, this infection was responsible for 30% of polyarteritis nodosa cases, but this number has dropped to 8% following aggressive vaccination efforts.

Many experts believe polyarteritis nodosa may be caused by immune system disorders, classifying it as an autoimmune disease. Autoimmune diseases occur when the body’s immune system, which normally attacks foreign organisms or pathogens, mistakenly attacks healthy tissue for unknown reasons.

Additionally, genetic abnormalities have been linked to a spectrum of vascular diseases, including polyarteritis nodosa. In these cases, the disease usually appears in childhood, often with a family history of similar conditions.

Risk Factor

Polyarteritis nodosa is more likely to occur in:

• Drug abuse, especially amphetamines
• Men, who are two to three times more likely to develop polyarteritis nodosa than women
• Those with a family history of polyarteritis nodosa

Symptoms

Polyarteritis nodosa primarily affects small and medium-sized arteries. Any organ's blood vessels can be involved, including those in the kidneys, heart, intestines, nerves, skin, and/or skeletal muscles. The arteries in the kidneys are most commonly affected, while the lungs are rarely involved.

Arterial damage can lead to increased blood pressure (hypertension), weakened arterial walls, causing dilation or aneurysms, blood flow blockages to tissues or organs, and tissue damage or death.

Early symptoms of polyarteritis nodosa resemble common viral infections, such as:

• Fever
• Fatigue
• Loss of appetite
• Muscle and joint pain, particularly in large joints

As polyarteritis nodosa progresses, symptoms depend on the affected organs, such as:

• Severe muscle and joint pain, which may last for weeks or months
• Night sweats
• Weight loss
• Abdominal pain
• Nausea and vomiting
• Bloody stools
• Skin rashes, red spots, painful bumps or sores, especially on the legs
• Testicular pain
• Numbness, tingling, or other changes in skin sensation, indicating nerve involvement
• Temporary vision disturbances in one eye
• Seizures
• Muscle weakness

Diagnosis

Early in the disease, the symptoms are not characteristic, often leading to delayed diagnosis. No specific blood or chemical tests can confirm polyarteritis nodosa. Diagnosis is based on physical examination and ruling out other diseases. If polyarteritis nodosa is suspected, a biopsy of the blood vessel wall is necessary. A definitive diagnosis is confirmed by biopsy showing areas of narrowing and dilation in small and medium arteries.

Additional tests may help detect organ involvement or identify potential causes of polyarteritis nodosa, such as:

• Blood tests to measure urea and creatinine levels, where elevated levels suggest kidney problems caused by polyarteritis nodosa
• Tests to detect hepatitis B or antibodies to hepatitis B in the blood to determine if hepatitis B is the trigger
• An arteriogram to reveal aneurysms or blockages in arteries leading to specific organs

Management

Treatment for polyarteritis nodosa typically involves medications to control the immune system and reduce inflammation, such as corticosteroids like prednisone. If corticosteroids alone are not effective, or if critical organs are involved, a combination of corticosteroids and cyclophosphamide may be used. Biological drugs like infliximab, etanercept, tocilizumab, tofacitinib, and rituximab may be used in recurrent cases. In severe cases, plasma exchange therapy has been tried.

Other treatments address underlying causes and manage symptoms. For polyarteritis nodosa associated with hepatitis B, antiviral medications (e.g., vidarabine, interferon alfa-2b) are given along with steroids and plasmapheresis. Treatment for hypertension may also be necessary. In some cases, particularly involving the gastrointestinal system, surgery may be required.

Complications

Polyarteritis nodosa can lead to complications, although it rarely causes permanent conditions. Possible complications include:

• Aneurysms that are prone to rupture, causing bleeding
• Blood clots block blood flow, leading to oxygen deprivation in tissues or organs, which can result in organ damage or tissue death, with consequences such as kidney failure, heart attack, heart failure, and stroke
• Nerve damage, particularly to the brain, which can be fatal in severe cases
• Gastrointestinal complications like bleeding or bowel perforation
• Inflammation of the heart’s lining (pericarditis)
• Pancreatic inflammation

Without treatment, polyarteritis nodosa can be fatal. Nearly half of patients die within 3 months of symptom onset. Death can result from heart attacks, strokes, or the immune suppression caused by treatment.

Prevention

There is no way to prevent most cases of polyarteritis nodosa. However, hepatitis B vaccination and avoiding activities that increase the risk of hepatitis infection, such as intravenous drug use or unprotected sex, can prevent hepatitis B infection.

When to See a Doctor?

If you experience symptoms of polyarteritis nodosa, you should consult a doctor. If you have chest pain, shortness of breath, severe abdominal pain, or a combination of these symptoms, seek medical attention immediately.

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