How is polyarteritis nodosa (PAN) treated?
Medications that suppress the immune system form the foundation of treatment for PAN. There are a variety of immunosuppressive medications that are used in PAN, each of which has individual side effects.
People with PAN who have critical organ system involvement are generally treated with a corticosteroid such as prednisone or prednisolone combined with another immunosuppressive medication such as cyclophosphamide (Cytoxan®). Cyclophosphamide is given at high doses as a treatment for certain types of cancer and therefore is sometimes referred to as "chemotherapy." In cancer treatment, cyclophosphamide works by killing or slowing the growth of rapidly multiplying cancer cells. In vasculitis, cyclophosphamide is given at doses that are 10 to 100 times lower than those used to treat cancer. In this setting, its primary effect is to influence the behavior of the immune system in a manner that results in immunosuppression. In rare instances, people who do not have manifestations affecting the nervous system, heart, kidneys, intestinal tract or other features of severe disease might do well with corticosteroid therapy alone.
All immunosuppressive medications can have side effects. Monitoring for side effects plays a critical role in preventing or minimizing their occurrence. Each medication has a unique side effect profile that forms the basis for the monitoring plan. The fact that someone with PAN may initially tolerate treatment does not guarantee that the person will have the same degree of tolerance over time. This makes ongoing monitoring essential, and in some instances, monitoring for long-term effects may be important even after the medication is stopped.
The goal of treatment is to eliminate features of inflammation due to PAN. When that is achieved it is referred to as "remission." Once it is apparent that the disease is improving, doctors slowly reduce the corticosteroid dose and eventually hope to discontinue it completely. When cyclophosphamide is used, it is often only given until the time of remission (usually around 3-6 months), after which time it may be switched to another immunosuppressive agent such as methotrexate or azathioprine (Imuran®) to maintain remission. The treatment duration of the maintenance immunosuppressive medication may vary between individuals. In most instances, it is given for a minimum of 1 to 2 years before consideration is given for whether it would be appropriate to slowly reduce the dosage to discontinuation.
In people who have a PAN-like vasculitis that is associated with hepatitis B, antiviral medications used to treat the hepatitis form an important part of care. Immunosuppressive agents are often given initially to control the vasculitis but may be withdrawn more quickly than in other settings so as to allow the anti-viral medications a better chance to control the infection.