Most Important Cutaneous Vasculitides
The most important cutaneous vasculitides to recognize are cutaneous leukocytoclastic angiitis (the most common form in adults), IgA vasculitis/Henoch-Schönlein purpura (most common in children), and the ANCA-associated vasculitides (Wegener granulomatosis/GPA, microscopic polyangiitis, Churg-Strauss syndrome/EGPA) which carry significant morbidity and mortality risk. 1, 2
Classification by Clinical Importance
Small Vessel Vasculitides (Highest Frequency)
Cutaneous Leukocytoclastic Angiitis (CLA)
- Most common cutaneous vasculitis in adults 1
- Presents as palpable purpura on lower extremities - this is nearly pathognomonic 3
- Up to 50% remain etiologically unexplained despite thorough workup 1
- Usually self-limited and resolves spontaneously 1
- Critical distinction: Can be isolated cutaneous disease OR herald systemic involvement
IgA Vasculitis (Henoch-Schönlein Purpura)
- Most common vasculitis in children 1
- Distinguished by IgA deposition on direct immunofluorescence - this is diagnostically crucial 4, 5
- Skin involvement often predominates even when systemic 2
- Can affect kidneys and GI tract with significant morbidity
ANCA-Associated Vasculitides (Highest Mortality Risk)
Granulomatosis with Polyangiitis (Wegener), Microscopic Polyangiitis, Eosinophilic Granulomatosis with Polyangiitis (Churg-Strauss) 6
- These require aggressive immunosuppression with corticosteroids plus cyclophosphamide due to high risk of permanent organ damage or death 4
- Cutaneous manifestations include palpable purpura PLUS nodules or livedo - this combination suggests ANCA-associated disease rather than simple immune complex vasculitis 3
- Coexistence of pan-dermal small-vessel and subcutaneous muscular-vessel vasculitis indicates ANCA-associated disease 4
Medium Vessel Vasculitides
Polyarteritis Nodosa (PAN) 6
- Systemic PAN: multiple manifestations including digital infarction, livedo racemosa, subcutaneous nodules 3
- Cutaneous PAN: predominantly subcutaneous nodules surrounded by livedo racemosa on lower legs 3
- Important because cutaneous form has better prognosis than systemic
Key Diagnostic Features That Determine Importance
Red Flags for Systemic Disease (High Morbidity/Mortality)
- Constitutional symptoms: weight loss, fever, exhaustion 1
- Ulcerative or necrotic lesions 7
- Hematuria (renal involvement) 7
- GI complaints 7
- Nodules or livedo in addition to purpura 3, 4
Histopathological Priorities
Obtain two biopsies when immune complex vasculitis suspected 5:
- For DIF: Early, partially blanchable macule - the type of perivascular immunoglobulin (IgA vs IgG/IgM) has prognostic significance 4, 5
- For routine histology: Most tender, reddish or purpuric lesion extending to subcutis 4
Serial sections often required to identify main vasculitic lesion 4
Clinical Pitfalls
Do not confuse vasculitis with vasculopathy (pseudovasculitis) 1, 4:
- Thrombotic disorders like antiphospholipid syndrome can mimic vasculitis clinically
- These require anticoagulation, NOT immunosuppression
- Histopathology distinguishes true vessel wall inflammation from thrombotic occlusion
Location matters for differential diagnosis 3:
- Lower extremity palpable purpura = immune complex small vessel vasculitis
- Cold-exposed area necrosis = consider cryoglobulinemic vasculitis
- Nailfold involvement = consider lupus or rheumatoid-associated vasculitis
- Extensor surface plaques = erythema elevatum diutinum
Secondary Causes Requiring Different Management
- Infections: Treat underlying infection
- Drugs: Discontinue offending agent
- Connective tissue diseases: Treat underlying CTD
- Malignancies: Address underlying cancer
The extent of diagnostic workup should be proportional to severity, duration, systemic symptoms, and recurrence 5 - not a blanket approach for all patients.