Polyarteritis Nodosa

Polyarteritis nodosa (PAN) is a rare, systemic autoimmune condition that causes inflammation of the blood vessels (i.e. vasculitis), specifically the medium-sized arteries. Arteries are blood vessels that carries blood from the heart to the rest of the body. The inflammation can damage the blood vessel walls, and lead to:
• Weakening and ballooning of the vessels affected 
• Narrowing of the vessel lumen or blockage of the blood flow to the organs they supply
• Organ damage due to lack of oxygen and nutrients (which are delivered via blood flow) – In PAN, the commonly affected organs are the gut, kidneys, skin and nerves. 

The cause of PAN is not fully understood, but it is thought to involve abnormal immune system activity that targets the walls of the medium-sized arteries, leading to inflammation and cell death. In many patients, no specific trigger is identified, but some known associations include:
• Infections especially chronic active hepatitis B
• Genetics: in rare inherited forms of PAN

PAN is rare and diagnosis can be challenging. Symptoms may vary among individuals, depending on the organs involved and severity of symptoms. Your doctor will look for evidence of blood vessel inflammation and distinguish this from other conditions that may appear similar to PAN. Diagnosis usually involves a combination of:
• Detailed history taking and physical examination
• Laboratory tests including blood counts, kidney function, inflammatory markers such as the Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) and urine tests. Other tests such as antibody tests and infection screens may be performed to rule out other conditions that may appear similar to PAN
• Imaging: Ultrasound, CT scan, MRI or PET-CT scans may be performed to look for any narrowing or ballooning of the vessels, as well as any inflammation around the blood vessel walls. The type of imaging modality depends on various factors such as the suspected blood vessels involved and patient factors such as the patient’s kidney function.
• A biopsy may be performed where appropriate to assess for inflammation in the arteries. This is helpful for diagnosis, but may not always be feasible.
• Additional tests may be done depending on the suspected organ involvement e.g. nerve conduction tests if there are concerns that the nerves are affected, cardiac echocardiogram for cardiac involvement etc.

PAN is a chronic condition that can be managed effectively with medications. The goal of treatment is to reduce inflammation, prevent damage to blood vessels, and preserve blood flow to vital organs. Prompt treatment is required once PAN is diagnosed as it can be life-threatening or cause permanent organ damage. Treatment is led by a rheumatologist and a multidisciplinary team of specialist doctors, depending on the organs involved. 

Treatment usually includes medications to suppress the inflammation and calm down the immune system. Patients with PAN will usually require long-term medications to control the disease and prevent relapse:
• Corticosteroids are fast-acting medications that effectively suppress the immune system. These are usually started at high doses (intravenous injections through the veins or oral), then reduced over time. 
• Immunosuppressive agents are used in addition to steroids to reduce the need for long-term steroids and for control of disease activity: Cyclophosphamide, azathioprine, methotrexate, etc
• Biologic agents are newer targeted medications given intravenously or subcutaneously into the abdomen or thighs. These may be used in patients who do not respond adequately to the above immunosuppressive agents. Examples include infliximab and adalimumab.

Antiviral therapy will be given if there is associated hepatitis B infection. Supportive treatment will be provided depending on the organ involvement e.g. pain management, wound care for cutaneous PAN, and blood pressure control.

Additionally, other medical conditions are addressed as part of holistic care, such as high cholesterol, diabetes, and osteoporosis. To prevent infections when on high doses of immune suppression medications, prophylactic antibiotics and certain vaccinations are encouraged (e.g. influenza, pneumococcal, COVID-19, shingles and respiratory syncytial virus). As multiple organ systems may be affected in PAN, patients are often cared for by a multidisciplinary team of medical professionals, including a primary rheumatologist and other relevant subspecialty teams and allied health professionals. Your treatment plan will be carefully tailored to your symptoms, preferences, and goals of care.

Patients with polyarteritis nodosa are able to live active lives with the right treatment and support. Some recommended lifestyle changes include:
• Eat a balanced diet. Avoid raw and partially cooked food to reduce risks of infections, especially if you are on medications that suppress the immune system (e.g. steroids).
• Avoid smoking.
• Stay active and exercise in moderation. Ensure sufficient rest and sleep well.
• Attend regular medical check-ups to monitor your health. Participate actively in your care and ask questions during your clinic consultations.
• Take your medications as prescribed, even when you feel well, to avoid disease flares.
• Seek medical attention early if you suspect a flare of PAN

Seek a doctor's advice. You will be referred to a specialist (rheumatologist) who can confirm the diagnosis and start you on the appropriate treatment. Once diagnosed, it is important to start treatment early and follow your rheumatologist’s advice. This condition is managed by the Division of Rheumatology and Allergy.