How should I treat a patient with cutaneous small‑vessel (leukocytoclastic) vasculitis limited to the lower leg, presenting with palpable purpura, pain, and swelling, and no known systemic disease?

Treatment of Cutaneous Small-Vessel Vasculitis Limited to the Lower Leg

For isolated cutaneous leukocytoclastic vasculitis limited to the lower leg without systemic involvement, begin with conservative management including leg elevation, NSAIDs, and observation, as this is frequently a self-limited disease; if symptoms persist or recur, initiate colchicine or dapsone as first-line agents. 1, 2

Initial Assessment and Exclusion of Systemic Disease

Before initiating treatment, you must systematically exclude systemic vasculitis and identify potential triggers:

• Obtain laboratory workup including complete blood count, ESR/CRP, kidney function, urinalysis with microscopy, complement levels (C3, C4), ANCA testing (MPO and PR3), cryoglobulins, and hepatitis B/C serology 1, 3
• Perform skin biopsy with both light microscopy and direct immunofluorescence to confirm leukocytoclastic vasculitis and exclude other diagnoses 4, 3
• Review all medications as drugs are a common trigger; discontinuation of the culprit agent is usually curative 3, 5
• Screen for infections and malignancy as potential underlying causes 3, 6

The key histopathologic features confirming leukocytoclastic vasculitis include fibrinoid necrosis, neutrophilic infiltration with nuclear fragmentation (leukocytoclasia), red blood cell extravasation, and endothelial cell damage 7, 3

Treatment Algorithm Based on Disease Severity

For Mild, Single-Episode Disease (First Presentation)

Conservative symptomatic management is appropriate as cutaneous small-vessel vasculitis is frequently self-limited 2, 4:

• Leg elevation and rest (avoiding prolonged standing or walking) 3
• NSAIDs for pain and inflammation 2, 5
• Antihistamines for associated pruritus 2
• Warming measures to improve circulation 2

If a medication or infection is identified as the trigger, removal or treatment of the inciting factor along with these symptomatic measures is often sufficient 4, 3

For Mild Recurrent or Chronic Disease

First-line systemic agents are colchicine or dapsone, used singly or in combination 2, 4:

• Colchicine is a first-choice agent for mild recurrent disease 2, 5
• Dapsone is equally effective as a first-line option 2, 4
• Low-dose prednisone (typically <20 mg/day) can be added if colchicine or dapsone alone are insufficient 2, 3

For Severe Cutaneous Disease or Refractory Cases

If the disease does not respond to first-line agents or causes severe symptomatic cutaneous involvement:

• Azathioprine (1-2 mg/kg/day) is an effective steroid-sparing immunosuppressive option 2, 4, 5
• Mycophenolate mofetil (2 g/day) is an alternative immunosuppressive agent 2, 4, 5
• Methotrexate can be considered for chronic refractory disease 4, 5
• Cyclosporine is reserved for difficult cases 4, 5
• Rituximab may be effective for truly refractory disease, though evidence is limited in isolated cutaneous vasculitis 4

Important caveat: Intravenous immunoglobulin (IVIG) and plasmapheresis are viable but cumbersome and expensive options reserved only for refractory disease unresponsive to conventional immunosuppression 2

Critical Distinction: Isolated Cutaneous vs. Systemic Vasculitis

This treatment approach applies ONLY to isolated cutaneous vasculitis without systemic involvement 1. If your workup reveals any of the following, the patient requires immediate aggressive immunosuppression as for systemic vasculitis:

• Positive ANCA with compatible clinical features (even if biopsy pending) 1
• Renal involvement (hematuria, proteinuria, rising creatinine) 8, 1
• Pulmonary involvement (hemoptysis, infiltrates, hypoxemia) 8
• Neurologic involvement (mononeuritis multiplex, motor neuropathy) 8
• Severe cutaneous disease (gangrene, extensive ulceration) 1

In these scenarios, treatment shifts to high-dose glucocorticoids (prednisone 1 mg/kg/day) combined with cyclophosphamide or rituximab, following systemic vasculitis protocols 8, 1

Common Pitfalls to Avoid

• Do not delay systemic workup: Approximately 10% of small-vessel vasculitis patients are ANCA-negative but still have systemic disease 1
• Do not assume isolated cutaneous disease: Mixed cryoglobulinemia (often HCV-related) can present with palpable purpura and requires specific treatment 8
• Do not use potent immunosuppression for truly isolated cutaneous disease: This exposes patients to unnecessary toxicity when conservative measures often suffice 2, 4
• Do not miss medication triggers: The prognosis is favorable when a drug is the cause, and discontinuation is usually curative 3