polyarteritis nodosa (PAN)

see also:

• vasculitis

• rare disease
• incidence of about 3-4.5 cases per 100,000 population annually
• males 2x females
• esp. ages 45-65yrs
• systemic vasculitis involving medium to small arteries
• most commonly affects skin, joints, peripheral nerves, the gut, and the kidney
• nodular skin lesions, neuropathy, and hypertension
• hepatitis B virus associated vasculitis almost always takes the form of PAN, and usually has onset in 1st 6 months of infection
  • HBV accounted for 30% of PAN but since widespread vaccination, it now only accounts for < 8% of cases
• many other infections and inflammatory diseases have been associated with possibly causing PAN including hepatitis C virus
• untreated, the 5-year survival rate of PAN is 13%
• corticosteroids treatment improves the 5-year survival rate to 50-60%
• adding immunosuppressants such as cyclophosphamide, the 5-year survival rate may increase to greater than 80%

• at least 3 of the 10 ACR criteria should be present when radiographic or pathological diagnosis of vasculitis is made:
  • weight loss of 4 kg or more
  • livedo reticularis
  • testicular pain/tenderness
  • myalgia or leg weakness/tenderness
  • mononeuropathy or polyneuropathy
  • diastolic blood pressure > 90 mm/Hg
  • levated blood urea nitrogen (BUN) or creatinine level unrelated to dehydration or obstruction
  • presence of hepatitis B surface antigen or antibody in serum
  • arteriogram demonstrating aneurysms or occlusions of the visceral arteries
  • biopsy of small- or medium-sized artery containing polymorphonuclear neutrophils

• full blood examination (FBE) - may have neutrophilia, normochromic anaemia, or thrombocytosis
• may have raised erythrocyte sedimentation rate (ESR) and/or C reactive protein (CRP) but may not correlate with disease activity
• U&E - may have raised creatinine
• check hepatitis B virus and hepatitis C virus serology
• urinalysis may show proteinuria
• liver function tests (LFTs) may be elevated
• 30% have hypergammaglobulinaemia
• ANCA is rarely positive
• ANA and Rh factor are generally negative or low titres
• CSF usually normal but may show polymorphonuclear pleocytosis if meningism present
• biopsy samples of skin nodules or ulcers should be collected at the edges and include deep dermis and subcutaneous fat
• biopsy of the sural nerve should be full-thickness to include epineural vessels
• consider angiography to demonstrate aneurysms or stenoses

• small and mid-size artery necrotizing vasculitis on biopsy with at least 2 of:
  • skin involvement (eg, livedo reticularis, tender subcutaneous nodules, other vasculitic lesions)
  • myalgia
  • systemic hypertension
  • mononeuropathy or polyneuropathy
  • abnormal urinalysis and/or impaired renal function (GFR < 50% normal for age)
  • testicular pain or tenderness
  • signs or symptoms suggesting vasculitis of any other major organ system (GI, cardiac, pulmonary, CNS)

• presence of subcutaneous nodular, painful, nonpurpuric lesions with or without livedo reticularis and absence of systemic involvement
• associated with streptococcus / streptococcal infections infection in 40%