Cutaneous Polyarteritis Nodosa (cPAN)

Localized polyarteritis nodosa; cPAN; Limited form of systemic PAN.

Cutaneous polyarteritis nodosa (cPAN) is a rare, chronic vasculitis of medium-sized arteries confined to the skin without systemic organ involvement. It is considered a limited form of classic systemic polyarteritis nodosa (PAN), with a predilection for the lower extremities.

Rare. Typically manifests in adults aged 30–50 years, with a slight female predominance. Pediatric cases are also reported. Exact incidence remains unclear.

Belongs to the group of medium-vessel cutaneous vasculitides (Chapel Hill Consensus 2012). Should be distinguished from systemic PAN and small-vessel vasculitis.

The exact cause is unknown. Likely an immune-mediated vasculitis of medium-sized arteries triggered by infections or immune dysregulation. Possible associations include:

• Streptococcal infections (particularly in children)
• Hepatitis B or C virus (less commonly than in systemic PAN)
• Immune complex–mediated mechanisms

• Painful subcutaneous nodules (typically on the lower legs)
• Net-like livedoid discoloration (livedo racemosa)
• Ulcers over nodules
• Necrosis, rarely bullae
• Arthralgia, myalgia
• Minimal systemic symptoms; no internal organ involvement

• Clinical: subcutaneous nodules, livedo, ulcers
• Biopsy (deep punch into subcutis):
  • Transmural necrotizing inflammation of medium-sized arteries
  • Mixed infiltrate (neutrophils, eosinophils, histiocytes)
  • Later: segmental fibrosis and vessel occlusion
• Laboratory tests:
  • Mild leukocytosis, elevated CRP/ESR possible
  • ANCA negative
  • Exclude systemic involvement (renal function, liver tests, chest imaging)

Predominantly lower extremities (shins, calves), less often arms or trunk.

Subacute onset of painful nodules and livedoid changes. Often relapsing–remitting. May follow streptococcal infection. Systemic signs absent.

Segmental necrotizing arteritis of medium-sized vessels in the dermis/subcutis with fibrinoid necrosis, transmural infiltrates, and muscular wall damage. In late stages: thrombosis, fibrosis.

• Painful ulcerations with risk of infection
• Recurrence with insufficient therapy
• Rare reports of transition to systemic PAN (controversial)
• Functional limitations due to pain or tissue loss

Generally favorable. Good long-term control with adequate therapy. Chronic–relapsing course possible. Prognosis significantly better than systemic PAN.

• Infection control (e.g., treatment of streptococcal tonsillitis)
• Regular clinical follow-up to detect systemic involvement
• Antibiotic prophylaxis in streptococcal-associated cases may be considered

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