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|Psoriasis
🧠 About
- Cutaneous small vessel vasculitis (CSVV), also called leukocytoclastic vasculitis, is the commonest form of vasculitis affecting the skin.
- It represents inflammation of dermal capillaries, venules, and arterioles leading to palpable purpura and, occasionally, ulceration or necrosis.
- It may be idiopathic or secondary to infection, drugs, autoimmune disease, or malignancy.
🧬 Aetiology & Pathophysiology
- Driven by immune complex deposition in post-capillary venules → complement activation → neutrophil infiltration and fibrinoid necrosis of vessel walls.
- Commonly associated with hypersensitivity reactions, infections, and autoimmune disorders.
- Histopathology shows: neutrophilic infiltrate, nuclear debris (leukocytoclasia), and fibrin deposition.
🎨 Clinical Features
- 🌸 Palpable purpura: non-blanching, raised purplish lesions, often on lower legs (gravity-dependent areas).
- Lesions may bleed, blister, ulcerate, or form necrotic plaques.
- May be associated with burning, pain, or pruritus.
- Livedo reticularis or petechial rash may coexist in chronic or recurrent cases.
- Systemic symptoms (arthralgia, abdominal pain, haematuria) may suggest systemic vasculitis.
🔍 Differential Diagnosis
- Thrombocytopenia or coagulopathy (non-palpable purpura).
- Scurvy (perifollicular haemorrhage).
- Meningococcaemia or rickettsial infections (febrile purpura).
- Drug eruptions and septic emboli.
⚗️ Common Causes
- 💊 Drugs: β-lactam antibiotics, thiazides, NSAIDs, allopurinol.
- 🦠 Infections: Streptococcus (ASO positive), Hepatitis B/C, HIV, Neisseria, Rickettsia, Meningococcus.
- 🧩 Autoimmune/Rheumatology: RA, SLE, Sjögren’s, Sarcoidosis.
- 🦠 Inflammatory Bowel Disease: Crohn’s, Ulcerative colitis.
- 🧫 Malignancy-associated: particularly haematological cancers (e.g. lymphoma).
🧪 Investigations
- Basic Screen: FBC, ESR/CRP, U&E, LFTs, urine dipstick for haematuria/proteinuria.
- Immunology: ANA, dsDNA, ENA, ANCA, complement (C3, C4), cryoglobulins.
- Infectious screen: Hepatitis B/C serology, HIV test, ASO titres, blood cultures.
- Systemic assessment: ACE level (sarcoidosis), serum electrophoresis, CXR.
- Diagnostic biopsy:
– Fibrinoid necrosis of dermal vessels
– Neutrophilic infiltrate with nuclear debris (leukocytoclasia)
– Extravasation of erythrocytes into dermis.
💊 Management
- 🎯 Treat underlying cause: Discontinue offending drug, treat infection or autoimmune disease.
- 🧍♀️ Supportive: Rest, leg elevation, compression stockings, emollients.
- 💊 Pharmacological:
– Mild: NSAIDs or antihistamines for symptomatic relief.
– Moderate: Colchicine or Dapsone (reduce neutrophil activation).
– Severe or systemic: Short course of oral corticosteroids (e.g. prednisolone 20–40 mg/day taper).
– Refractory: Immunosuppressants (azathioprine, methotrexate, or mycophenolate) under specialist care.
- 🩺 Monitor for renal, GI, or neurological involvement (suggests systemic disease).
📊 Prognosis
- Most idiopathic or drug-induced cases resolve within 4–6 weeks.
- Recurrence may occur if the trigger persists or in autoimmune disease.
- Chronic or ulcerating forms require multidisciplinary input (dermatology, rheumatology).
💡 Teaching Tip
- Always differentiate between cutaneous-only vs systemic vasculitis - systemic cases need urgent evaluation for renal or pulmonary involvement.
- Histology confirms the diagnosis - biopsy new lesions (24–48 hrs old) for the best yield.
- In teaching, contrast this with Henoch–Schönlein Purpura (IgA vasculitis) - identical pathology, but with systemic IgA deposition (esp. renal).
📚 References
- BNF: Systemic Corticosteroids & Immunomodulators
- Jennette JC et al., Arthritis Rheum 2013;65:1–11 - Chapel Hill Consensus Classification.
- Genta RM, Mod Pathol 1990;3(3):282–296 - Cutaneous small vessel vasculitis histology.
- DermNet NZ: Leukocytoclastic Vasculitis (2023).
