Polyarteritis Nodosa (PAN) is a rare disease that affects the blood vessels causing swelling called vasculitis. It is considered to be an autoimmune condition and involves inflammation of medium-sized arteries, affecting various organs and tissues throughout the body. 

Introduction

Polyarteritis nodosa, also known as PAN, is a rare disease caused by inflammation of the blood vessels. Blood vessel inflammation is called vasculitis and can lead to injury to the organ systems. Polyarteritis Nodosa affects medium-sized blood vessels.

When a blood vessel becomes inflamed, it may weaken and expand, potentially resulting in aneurysms, or it may become so thin that it bursts and leaks blood into the surrounding tissue. Vasculitis can also result in blood artery narrowing to the point of complete closure, which damages organs by depriving them of oxygen and nutrients that the blood supplies.

The areas that are most commonly affected by polyarteritis nodosa include the nerves, digestive system, the heart, and the joints. PAN can affect the blood vessels going to the kidney resulting in high blood pressure and damage to kidney function.

As many systems can be affected, the symptoms are wide-ranging. PAN is a rare disease and is more frequent in men than in women. Polyarteritis nodosa can occur in people of all ages however, idiopathic systemic PAN occurs most frequently in middle-aged people in their 40s to 60s.¹

Causes of polyarteritis nodosa

The exact cause of primary polyarteritis nodes is unknown. Research indicates that the involvement of the body's immune system in PAN, results in tissue and blood vessel inflammation and damage. Hepatitis infection and PAN have a strong correlation.

This is known as secondary polyarteritis nodosa. Secondary PAN is less frequent and seen in people with hepatitis B, hepatitis C, and in some malignancies. PAN rates have dramatically declined since the hepatitis B vaccination was developed.

In addition to hepatitis B, several other infections, such as Yersinia species, trichinosis, Toxoplasma, Pseudomonas, Klebsiella, and parvovirus B-19, have also been connected to PAN. Polyarteritis nodosa is also connected to hairy cell leukaemia, rheumatoid arthritis, and Sjogren syndrome.²

Clinical presentation of polyarteritis nodosa

Because many different organ systems may be involved, a wide range of symptoms are possible in polyarteritis nodosa. PAN presents with a range of symptoms, some of which are nonspecific and can overlap with other conditions.

Recognizing these symptoms is crucial for an accurate diagnosis. The common symptoms seen in PAN include fever, fatigue, muscle and joint pain, and weight loss. People with PAN may also have organ-specific symptoms depending on the areas involved. These can include:

• Skin manifestations: PAN can cause various skin issues, including rashes, nodules, and purpura. These skin changes often serve as visible indicators of the disease's presence
• Nervous system involvement: Neuropathy, or damage to the nerves, can result in symptoms such as pain, weakness, and sensory disturbances. In severe cases, nervous system involvement can lead to more serious complications
• Gastrointestinal symptoms: PAN's impact on the gastrointestinal system may lead to abdominal pain, nausea, vomiting, and in some cases, bowel perforation
• Renal system: The kidney is the most commonly affected organ. Swelling of arteries supplying blood to the kidney can lead to aneurysms and rupture²

Diagnosis of polyarteritis nodosa

Polyarteritis nodosa is a multisystemic disorder and can produce a variety of symptoms common to other conditions such as infection or malignancy. Diagnosing polyarteritis nodosa is primarily based on clinical findings, imaging, and histopathological investigations.¹ Diagnosing PAN involves a combination of medical history, physical examination, and various diagnostic tests.

Clinical assessment involves a medical history to look for the presence of PAN symptoms and a physical examination to detect sites of organ involvement and to exclude other illnesses that may have a similar appearance. Blood tests and urinalysis are used to look for signs of organ involvement. Once the diagnosis of PAN is suspected, confirmation of the diagnosis is usually pursued by obtaining an arteriogram or a biopsy.

The diagnosis is generally confirmed by tissue biopsy of an affected organ. A deep skin biopsy specimen is suggested if skin involvement is present.³ Biopsies show swelling in medium-sized arteries while small arteries, arterioles, and capillaries are spared. When PAN is highly suspected and a histologic diagnosis of vasculitis cannot be made through biopsy, or when a patient's symptoms mostly point to abdominal, renal, or cardiac involvement, angiography may be carried out.⁴

Treatment of polyarteritis nodosa

Medications that suppress the immune system form the foundation of treatment for polyarteritis nodosa. There is a variety of immunosuppressive medications that can be used in PAN. Once diagnosed, the management typically involves a combination of immunosuppressive medications and supportive care.

Steroids: Corticosteroids, such as prednisone, are commonly used to suppress the immune response and reduce inflammation in PAN. In more severe cases or when corticosteroids alone are insufficient, additional immunosuppressive medications may be prescribed. These may include cyclophosphamide, methotrexate, or rituximab.

Antivirals: People with PAN associated with hepatitis B or C infection also benefit from treatment with anti-viral medication (such as currently lamivudine or adefovir). Treatment with antivirals should occur before any immunosuppressive medications are added.⁴

Anti-hypertensive: Angiotensin-converting enzyme (ACE) inhibitors are a treatment option for hypertension. The renin-angiotensin system is thought to be the mechanism by which PAN-related hypertension is mediated. But renal function needs to be continuously watched, and renal function is affected, a different medication, such as calcium channel blockers, needs to be taken.²

Supportive care: While immunosuppressive medications target the underlying cause of PAN, supportive care aims to alleviate symptoms and improve the patient's overall well-being. Pain management, physical therapy, and other supportive measures may be incorporated into the treatment plan.

Long-term management: PAN is often a chronic condition that requires long-term management. Regular follow-up appointments with healthcare providers are essential to monitor disease activity, adjust medications as needed, and address any emerging symptoms or complications. A multidisciplinary approach involving rheumatologists, dermatologists, and other specialists may be employed to provide comprehensive care.

Complications of polyarteritis nodosa 

Complications associated with PAN may include organ damage, such as kidney or nerve damage, and an increased risk of infections due to immunosuppressive therapy. Timely and appropriate medical intervention can help mitigate these complications and improve the overall prognosis.

Living with PAN can pose challenges, both physically and emotionally. Chronic pain, fatigue, and the uncertainty of the disease's course can affect the quality of life for individuals with PAN. Support from healthcare professionals, family, and support groups can play a crucial role in addressing these challenges.

Prognosis of polyarteritis nodosa

Given the high likelihood of relapse in PAN patients, long-term monitoring is essential. Furthermore, it's possible that further organs will be affected, and the immunosuppressive medication dosage needs to be adjusted. People with PAN are vulnerable to infections due to being on immunosuppression Relapses are common in PAN and often happen after five years.

The prognosis for PAN is poor if left untreated, yet treatment has made a major difference in results. Kidney failure, heart, or brain infarction are the leading causes of mortality. Most importantly, there is a bad prognosis if the central nervous system is involved, and recovery is slow. 

The prognosis for those with abdominal involvement is equally bad due to the possibility of perforations. People with skin involvement have the best prognosis, but there is still a chance of relapse. Individuals with PAN secondary to Hepatitis B typically heal and have a minimal chance of relapsing.²

Summary

In conclusion, polyarteritis nodosa is a complex and rare disease characterized by swelling of medium-sized arteries. The exact cause of PAN remains unknown, but it is generally considered an autoimmune disorder This complex condition can affect various organs and tissues throughout the body.

Its diverse clinical presentation, ranging from skin manifestations to neurological symptoms, underscores the importance of a multidisciplinary approach to diagnosis and management. Treatment of PAN is guided by disease severity and the organs involved. In most cases, management is a combination of immunosuppressive therapy and supportive measures.