What are the diagnostic criteria and treatment options for polyarteritis nodosa?

Diagnosis of Polyarteritis Nodosa

For diagnosing polyarteritis nodosa (PAN), a combination of clinical features, vascular imaging, and tissue biopsy is required, with abdominal vascular imaging and deep tissue biopsies being the most valuable diagnostic tools. 1

Diagnostic Criteria

The diagnosis of PAN typically requires:

1. Characteristic clinical features:

   • Systemic symptoms: fever, weight loss
   • Peripheral neuropathy (present in 50-75% of patients)
   • Skin lesions
   • Hypertension
   • Abdominal pain 1, 2

2. Laboratory findings:

   • Elevated inflammatory markers (ESR, CRP)
   • Possible hepatitis B surface antigenemia (in HBV-associated PAN) 1, 3

3. Imaging studies:

   • Abdominal vascular imaging is conditionally recommended as a first-line diagnostic tool 4
   • Options include:
     • Conventional catheter-based angiography
     • CT angiography
     • MR angiography 1, 5
   • Look for characteristic saccular or fusiform aneurysms and stenotic lesions 1
   • The presence of aneurysms correlates with more severe disease 3

4. Tissue biopsy:

   • Deep-skin biopsy (reaching medium-sized vessels of the dermis) is conditionally recommended over superficial skin punch biopsy when skin involvement is suspected 4, 1
   • Combined nerve and muscle biopsy is conditionally recommended over nerve biopsy alone when peripheral neuropathy is present 4, 1
   • Histopathology should show necrotizing inflammation of medium-sized vessels 6

5. Exclusion of other vasculitides 1

Disease Classification

PAN can be categorized based on severity:

• Severe disease: Life- or organ-threatening manifestations including:

  • Renal disease
  • Mononeuritis multiplex
  • Muscle disease
  • Mesenteric ischemia
  • Coronary involvement
  • Limb/digit ischemia 4

• Nonsevere disease: Without life- or organ-threatening manifestations:

  • Mild systemic symptoms
  • Uncomplicated cutaneous disease
  • Mild inflammatory arthritis 4

Treatment Approach

Treatment varies based on disease severity:

For Severe PAN:

1. First-line therapy:

   • IV pulse glucocorticoids (methylprednisolone 500-1,000 mg/day for adults or 30 mg/kg/day for children for 3-5 days)
   • Followed by high-dose oral glucocorticoids (prednisone 1 mg/kg/day for adults or 1-2 mg/kg/day for children)
   • Plus cyclophosphamide, which is conditionally recommended over glucocorticoids alone 4, 1

2. Alternative therapy (for cyclophosphamide intolerance):

   • Other non-glucocorticoid immunosuppressive agents with glucocorticoids 1

For Nonsevere PAN:

• Non-glucocorticoid immunosuppressive agents with glucocorticoids 1

For HBV-associated PAN:

• Antiviral therapy combined with plasma exchange 6, 2

Monitoring and Follow-up

1. For peripheral neuropathy:

   • Serial neurologic examinations are preferred over repeated electromyography/nerve conduction studies 4, 1

2. For abdominal involvement:

   • Follow-up abdominal vascular imaging is recommended for patients with a history of severe PAN with abdominal involvement who become asymptomatic 4, 1

3. After achieving remission:

   • Continue non-glucocorticoid immunosuppressive agent for approximately 18 months
   • Gradual glucocorticoid taper based on clinical condition 1

Prognosis

• Untreated severe PAN has a mortality rate of 40% at 5 years
• Early recognition and prompt treatment significantly improve outcomes 1
• The incidence of PAN is decreasing due to prevention of hepatitis B virus infection 1, 6

Important Considerations

• The presence of aneurysms on imaging correlates with severe hypertension, hepatitis B surface antigenemia, and clinically severe disease 3
• Peripheral neuropathy is one of the earliest and most frequent symptoms (50-75% of patients) 2
• Central nervous system involvement is rare (2-10% of patients) and often occurs late in the disease course 2
• Misdiagnosis can lead to inappropriate treatment and worse outcomes 1