Polyarteritis Nodosa Treatment & Management

The treatment of polyarteritis nodosa (PAN) has improved dramatically. Previously, untreated PAN was usually fatal within weeks to months, with mortality often associated with kidney failure, cardiac complications, or GI complications. Therefore, early diagnosis and treatment are critical in PAN.

Currently, corticosteroids are the cornerstone of treatment. The addition of cyclophosphamide is the standard of care for patients with idiopathic PAN whose disease is steroid refractory or includes major organ involvement. This combination can provide prolonged survival for these patients. In contrast, for hepatitis B–related PAN, treatment consists of schemes that include corticosteroids with antiviral agents and plasmapheresis. Cyclophosphamide is not routinely recommended in hepatitis B–related PAN as the use of steroids with cyclophosphamide in these patients has been demonstrated to enhance viral replication. Antiviral drugs used include vidarabine or interferon alpha-2b.

Surgical care

Surgery may be necessary for GI manifestations of PAN, including bowel ischemia, cholecystitis, and appendicitis. Microcoil embolization of cerebral aneurysm may be indicated. Postsurgical care may be needed for patients with PAN who develop bowel infarction.

The optimal management for polyarteritis nodosa (PAN) has not been established. Trial results in PAN are difficult to interpret, as many were conducted prior to the creation of the CHCC definition and included patients with MPA and Churg-Strauss syndrome. Corticosteroids have shown a clear benefit in these vasculitides, resulting in improvement of 5-year survival rates to 50%.^[28] Cyclophosphamide may improve the survival rate in patients with severe disease.^[29]

Glucocorticoids

No standard regimen for steroid dosing exists in PAN. It is common practice to use high-dose oral prednisone at 1 mg/kg/day.^[29] Methylprednisolone could also be given, for example, at a pulse dose of 1,000 mg intravenously daily, repeated over 3 days, prior to initiating oral prednisone.

Tapering of the prednisone can begin as early as one month later if the patient's clinical status and ESR normalize. Prednisone taper can continue over the next 12 months until it has been stopped.

When prednisone is combined with cyclophosphamide, the steroid dose is tapered more rapidly, if possible, to reduce the increased risk of infection.

Cyclophosphamide

Cyclophosphamide therapy may be initiated in patients with serious involvement of major organs or steroid-refractory PAN.^[5] Cyclophosphamide can be given as a monthly intravenous (IV) pulse or as a daily pill. IV pulse cyclophosphamide has a rapid onset of action, allows a lower cumulative dose to be administered, and exposes the patient to potential toxicity for shorter periods than an oral regimen. In some cases, however, daily oral cyclophosphamide is needed for a satisfactory therapeutic response.

Administration of IV or oral cyclophosphamide requires close monitoring of blood counts and renal function. Dosing should be adjusted accordingly.

Potential toxicities of cyclophosphamide to be discussed with patients include an increased risk of bladder cancer, hematologic malignancies, hemorrhagic cystitis, bladder fibrosis, bone marrow suppression, and gonadal failure.

Guillevin et al suggested that patients with a 5-factors score (FFS) of zero may be treated successfully with corticosteroids alone, with cyclophosphamide administered only as second-line treatment in cases of persistent disease, relapse, or inability to taper steroids. They recommend that, cyclophosphamide should be part of the initial regimen in combination with steroids in patients with an FFS of 1 or more.^[22]

Therapy with steroids and cyclophosphamide places patients at high risk for infections. Prophylaxis for Pneumocystis jiroveci pneumonia (PCP) is encouraged in these patients.

Patients receiving long-term steroid therapy are at risk for glucocorticoid-induced osteoporosis. Calcium and vitamin D supplementation should be given. Bisphosphonates are indicated in patients in whom glucocorticoids are being initiated.

For cutaneous PAN, methotrexate, azathioprine, and mycophenolate mofetil are sometimes effective therapeutic options after remission is achieved.^[30]

HBV-related PAN

PAN in the setting of HBV infection is a special situation. Standard therapies for PAN, including glucocorticoids and cyclophosphamide, enhance prognosis and control of the polyarteritis. However, they are also associated with persistent HBV infection and failure to seroconvert from hepatitis B surface antigen to hepatitis B surface antibody and from hepatitis B e antigen to hepatitis B e antibody. Thus, antiviral medications are essential in the treatment of these patients.

Guillevin and colleagues studied therapeutic strategies, including steroids, antivirals, and plasma exchange (plasmapheresis), and found the regimens below to be successful.^[31]

Prednisone (1 mg/kg/d) is administered for the first week. Alternatively, methylprednisolone pulse (15 mg/kg/d for 1-3 d) is used in severely ill patients. Steroids are then tapered rapidly and withdrawn at the end of week two.

Antiviral agents are begun after steroid withdrawal to enhance immunologic clearance of HBV-infected hepatocytes and favor seroconversion. Agents studied included vidarabine,^[32] which was replaced by interferon-α2b,^[33] and later by lamivudine.^[31] It is recommended that lamivudine be continued for 6 months or stopped at the time of seroconversion to hepatitis B surface antibody. (These recommendations may change; combination treatment and prolonged courses of antivirals are currently being investigated in the management of HBV).

Plasma exchanges are used as adjunctive therapy with antivirals. Plasma exchange is performed 3 times per week for 3 weeks, twice weekly for 2 weeks, and then once weekly. Plasma exchanges are stopped once seroconversion from hepatitis B e antigen to hepatitis B e antibody occurs or after clinical recovery is maintained for 2-3 months.

Isolated case reports have demonstrated benefit from the combination of interferon-α2b and lamivudine^{[34, 35]} or the addition of famciclovir and granulocyte-macrophage colony-stimulating factor in patients in whom antiviral therapy alone could not seroconvert and clear their HBV infection.^[36]

Critically ill patients who are not responding to treatment may require prolonged steroids and cyclophosphamide in the setting of lamivudine therapy.^[31]

Consultation with a rheumatologist is appropriate. Other consultants should be sought according to organ system involvement and include the following:

• Cardiologist
• Gastroenterologist
• Dermatologist
• Nephrologist
• Neurologist
• Physiatrist - Physical and occupational therapies are initiated promptly; once the patient's condition is stable, ambulation and maximization of activities of daily living are the chief goals

Patients with polyarteritis nodosa (PAN) should be monitored closely for evidence of relapse or symptoms indicating new organ involvement. Cyclophosphamide dosing should be adjusted according to the level of immunosuppression. The patient’s complete blood count (CBC) should be checked 10-14 days after IV cyclophosphamide is administered and every 2 weeks once oral cyclophosphamide is initiated.