Info
🌱 來自: Huppert’s Notes
Small Vessel Vasculitis Immune-Complex Mediated🚧 施工中
Small Vessel Vasculitis: Immune-Complex Mediated
Palpable purpura on exam, leukocytoclastic vasculitis on skin biopsy
Cryglobulinemic vasculitis
• Pathogenesis: Immune complex-mediated small vessel vasculitis caused by Ig molecules that precipitate at temperatures lower than 37ºC, known as cryoglobulins. Types of cryoglobulins:
- Type I – IgM rheumatoid factor associated with multiple myeloma
- Type II and III – “Mixed cryoglobulinemia” because the precipitating antibodies are a mixture of polyclonal IgG and either:
• Polyclonal IgM rheumatoid factor (Type II)
• Monoclonal IgM rheumatoid factor (Type III)
• Diagnosis:
- 90% of cases of mixed cryoglobulinemia are associated with HCV infection (test for HCV if cryos are identified!), but SLE and Sjögren’s can also cause Type III
- Additional lab findings include +Rf and very low C4
- Pearl about sample collection: Must keep at >37°C to avoid premature precipitation and false negative result
• Clinical features:
- Derm (70–90%): Palpable purpura, Raynaud’s, ulcers, skin necrosis, livedo reticularis
- Neuro (60%): Distal symmetric polyneuropathy
- Arthritis (40%)
- Renal (40%): Immune complex glomerulonephritis
• Treatment:
- Treat HCV or control the underlying rheumatic disease (e.g., Sjögren’s or SLE)
- For organ-threatening disease such as acute renal failure, plasmapheresis or glucocorticoids plus rituximab or cyclophosphamide are options
IgA vasculitis (Henoch-Schönlein purpura, HSP)
• Epidemiology: Childhood vasculitis that rarely occurs in adults with incidence of 14/million individuals annually
• Clinical features: Often preceded by viral URI or strep pharyngitis. Main manifestations include small vessel luminal vasculitis causing abdominal pain, GIB (65%), arthritis and arthralgias (63%) and glomerulonephritis (40%).
• Diagnosis: Gold standard is skin biopsy with leukocytoclastic vasculitis and heavy IgA deposits, or renal biopsy showing IgA nephropathy
• Treatment:
- Self-limited in children
- Adults may require glucocorticoids and/or cyclophosphamide for severe organ-threatening disease
Hypersensitivity vascultiis
• Clinical features: A small vessel vasculitis with isolated cutaneous involvement (palpable purpura) triggered by exposure to a known or unknown antigen
• Diagnosis:
- Skin biopsy shows leukocytoclastic vasculitis without IgA staining in the correct clinical context
- Typically, the vasculitis will resolve 7–10 days after removal of the offending antigen. Persistent symptoms for more than a month should raise suspicion for the presence of an alternative diagnosis
• Treatment: Removal of the offending antigen