What is the appropriate management for a patient with purpuric lesions spreading from the right ankle to the entire right leg, right abdomen, and left thigh?

Management of Spreading Purpuric Lesions

This patient requires immediate hospitalization with urgent dermatology consultation and skin biopsy to differentiate between life-threatening Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), purpura fulminans, or vasculitic processes, as the spreading pattern and extent of involvement demand rapid diagnosis and treatment to prevent mortality and severe morbidity. 1, 2

Immediate Assessment and Stabilization

Critical Initial Evaluation

• Assess body surface area (BSA) involvement to determine severity: spreading from ankle to entire leg, abdomen, and contralateral thigh suggests >30% BSA involvement, which would classify as grade 4 toxicity if SJS/TEN or severe disease if vasculitic 1
• Check for skin tenderness, pain, and Nikolsky sign (gentle lateral pressure causing epidermis to slide over dermis) which indicates epidermal necrolysis and SJS/TEN 1
• Examine for mucosal involvement (eyes, mouth, nose, genitalia) as erosive hemorrhagic mucositis is an early feature of SJS/TEN and helps differentiate from other causes 1
• Assess vital signs and hemodynamic stability as purpura fulminans presents with high fever (mean 104°F), hypotension, and altered mental status in severe cases 3, 2

Essential Immediate Laboratory Testing

• Complete blood count with peripheral smear to assess for thrombocytopenia, schistocytes, and disseminated intravascular coagulation (DIC) 4, 5, 2
• Coagulation studies including PT/INR, PTT, fibrinogen, and D-dimer to evaluate for DIC and purpura fulminans 3, 2
• Renal and liver function tests to assess for systemic involvement and guide treatment decisions 5
• Antiphospholipid antibodies and antinuclear antibodies if vasculitis or thrombotic microangiopathy suspected 1, 5

Diagnostic Procedures

Urgent Skin Biopsy

• Perform punch biopsy from the edge of a purpuric lesion including normal-appearing skin for both H&E staining and direct immunofluorescence 5, 6
• Request direct immunofluorescence to identify IgA and C3 deposits (Henoch-Schönlein purpura) or other immune complex deposition patterns 6, 7
• Clinical photography should be obtained to document extent and progression 1

Differential Diagnosis Considerations

Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis:

• Characterized by widespread purpuric macules or flat atypical targets with tender skin and positive Nikolsky sign 1
• Prodrome of fever, malaise, and upper respiratory symptoms precedes eruption by several days 1
• Cutaneous pain is a prominent early feature that should alert to incipient epidermal necrolysis 1

Purpura Fulminans:

• Catastrophic syndrome with purpuric ecchymosis, high fever, hypotension, DIC, and potential gangrene of extremities 3, 2
• Typically occurs 1-4 weeks after infectious process in children, but can occur in adults 3
• Platelet counts markedly depressed in fatal cases (survivors have mean platelet count 370,000) 3

Henoch-Schönlein Purpura:

• Palpable purpuric rash (without thrombocytopenia) with potential arthritis and abdominal pain 7
• More common in children but adults have higher complication rates 7
• Skin biopsy shows leukocytoclastic vasculitis with IgA and C3 deposits 6, 7

Treatment Algorithm Based on Diagnosis

If SJS/TEN Suspected (Grade 4 with >30% BSA)

• Immediately discontinue all potential causative medications 1
• Initiate IV methylprednisolone 1-2 mg/kg for grade 4 skin toxicity with skin sloughing >30% BSA 1
• Transfer to specialized dermatology unit or burn unit for supportive care 1
• Do not restart checkpoint inhibitors if this is immunotherapy-related 1

If Purpura Fulminans Suspected

• Immediate heparinization with continuous heparin drip to prevent subsequent small vessel thrombosis and limit tissue loss 3, 2
• Protein C replacement therapy if available, particularly if congenital protein C deficiency suspected 1, 2
• Aggressive supportive care including IV antibiotics for underlying infection, hemodynamic support, and management of DIC 3, 2
• Conservative management of purpuric lesions until final demarcation occurs; avoid early surgical intervention 3

If Henoch-Schönlein Purpura or Vasculitis Suspected

• Oral prednisone 1-2 mg/kg daily for two weeks for abdominal and joint symptoms 7
• Supportive treatment as primary intervention since 94% of children and 89% of adults have spontaneous resolution 7
• Monitor renal function closely as 40-50% develop renal disease and long-term prognosis depends on severity of renal involvement 7

Critical Pitfalls to Avoid

• Do not delay skin biopsy waiting for laboratory results, as histopathology is crucial for definitive diagnosis 5
• Do not transfuse platelets for isolated thrombocytopenia without active bleeding, as this is not indicated in ITP or vasculitic processes 4, 8
• Do not perform early surgical debridement in purpura fulminans until final tissue demarcation occurs 3
• Do not continue potential causative drugs if SJS/TEN is in the differential diagnosis 1
• Avoid platelet antibody testing as it lacks sensitivity and specificity for diagnosis 4

Monitoring and Follow-up

• Daily assessment of BSA involvement and progression of lesions 1
• Serial complete blood counts and coagulation studies if DIC suspected 3, 2
• Renal function monitoring particularly if Henoch-Schönlein purpura or systemic vasculitis diagnosed 7
• Ophthalmology consultation if mucosal involvement present in SJS/TEN 1