What is the appropriate diagnostic and treatment approach for a patient presenting with cutaneous vasculitis (vasculitic rash)?

Diagnostic and Management Approach to Cutaneous Vasculitis

The diagnostic approach to cutaneous vasculitis requires a skin biopsy extending to the subcutis from the most tender, reddish, or purpuric lesional skin as the key to obtaining a significant diagnostic result, followed by appropriate laboratory testing and treatment based on disease severity.

Clinical Presentation

• Most common presentation: Palpable purpura or infiltrated erythema (indicating dermal superficial, small-vessel vasculitis)
• Less common presentations:
  • Nodular erythema
  • Livedo racemosa
  • Deep ulcers
  • Digital gangrene (implicating deep dermal or subcutaneous, muscular-vessel vasculitis)
  • Urticaria
  • Hemorrhagic vesicles
  • Infarcts

Diagnostic Approach

Step 1: Skin Biopsy (Essential)

• Obtain biopsy from most tender, reddish or purpuric lesional skin
• Extend to subcutis to identify the main vasculitic lesion 1
• Request serial sections to maximize diagnostic yield
• Perform concomitant biopsy for direct immunofluorescence (DIF) to:
  • Distinguish IgA-associated vasculitis (Henoch-Schönlein purpura) from IgG/IgM-associated vasculitis
  • Identify immune complex deposition patterns

Step 2: Laboratory Investigations

• Complete blood count with differential
• Comprehensive metabolic panel
• Inflammatory markers (ESR, CRP)
• Urinalysis with microscopic examination
• ANCA testing (both MPO-ANCA and PR3-ANCA) using high-quality antigen-specific assays 2
• Consider additional tests based on clinical suspicion:
  • Cryoglobulins
  • Complement levels (C3, C4, CH50)
  • Hepatitis B and C serologies
  • ANA and other autoimmune markers
  • Blood cultures if infection suspected

Step 3: Imaging (When Systemic Involvement Suspected)

Select imaging based on suspected vessel size:

• Large vessels: CT/CTA, MRI/MRA, or FDG-PET/CT
• Medium vessels: CTA of affected regions (renal, mesenteric, coronary)
• Small vessels: MRI/MRA or FDG-PET/CT 2

Classification and Etiology Assessment

1. Primary vasculitis:

   • Idiopathic cutaneous leukocytoclastic angiitis
   • ANCA-associated vasculitis (GPA, EGPA, MPA)
   • IgA vasculitis (Henoch-Schönlein purpura)
   • Urticarial vasculitis
   • Erythema elevatum diutinum

2. Secondary vasculitis:

   • Connective tissue diseases (SLE, rheumatoid arthritis)
   • Infections
   • Drug-induced
   • Malignancy-associated
   • Cryoglobulinemia

Treatment Algorithm

Step 1: General Measures (For Mild, Limited Disease)

• Leg elevation
• Avoidance of prolonged standing
• Avoidance of cold temperatures and tight-fitting clothing
• NSAIDs for symptomatic relief 1, 3

Step 2: First-Line Pharmacologic Therapy (For Mild Recurrent or Persistent Disease)

• Colchicine (0.6 mg 1-2 times daily)
• Dapsone (50-200 mg daily)
• These can be used singly or in combination 4

Step 3: Moderate to Severe Disease

• Systemic corticosteroids (prednisone 0.5-1 mg/kg/day) 2, 3
• Consider adding steroid-sparing agents early:
  • Azathioprine (1-2.5 mg/kg/day)
  • Methotrexate (15-25 mg weekly)
  • Mycophenolate mofetil (1-3 g daily)

Step 4: Severe or Systemic Vasculitis

• High-dose corticosteroids (prednisone 1 mg/kg/day)
• Plus one of the following:
  • Cyclophosphamide (up to 2 mg/kg/day oral or intermittent IV)
  • Rituximab (375 mg/m² IV weekly for 4 doses or 1,000 mg on days 1 and 15) 2

Step 5: Refractory Disease

• Plasmapheresis
• Intravenous immunoglobulin
• Consider biologic therapies:
  • TNF-alpha inhibitors (e.g., infliximab)
  • Anti-B-cell therapy (rituximab) 1, 3

Monitoring and Follow-up

• Regular monitoring should include:

  • Renal function tests
  • Urinalysis with microscopic examination
  • Inflammatory markers
  • ANCA levels (if initially positive)
  • Complete blood count with differential 2

• Disease activity assessment using:

  • Birmingham Vasculitis Activity Score
  • Disease Extent Index
  • Vasculitis Damage Index 2

Important Considerations

• Do not delay treatment while waiting for biopsy results in ANCA-positive patients with compatible clinical presentation, especially in rapidly deteriorating patients 2
• Coexistence of pan-dermal small-vessel vasculitis and subcutaneous muscular-vessel vasculitis usually indicates CTD, ANCA-associated vasculitis, Behçet disease, or malignancy-associated vasculitis 1
• Exclude vasculitis-like syndromes (pseudovasculitis) such as thrombotic disorders (e.g., anti-phospholipid antibody syndrome) 1
• In most instances, cutaneous vasculitis represents a self-limited, single-episode phenomenon, but severe cases require prompt and aggressive treatment 3, 5