A 42-year-old woman with a 10-year history of rheumatoid arthritis presents with palpable purpura on the lower extremities and glomerulonephritis. Which is the most common type of vasculitis in patients with established rheumatoid arthritis?

Explanation

## Rheumatoid Vasculitis: The Most Common Vasculitis in RA **Key Point:** Rheumatoid vasculitis is a small-vessel vasculitis that is the most common form of vasculitis occurring in patients with established rheumatoid arthritis, typically in those with severe, long-standing, seropositive disease. ### Epidemiology and Risk Factors **High-Yield:** Rheumatoid vasculitis occurs in 1–5% of RA patients, but is more common in those with: - Long disease duration (>10 years) - High-titer rheumatoid factor (RF) and anti-CCP antibodies - Extra-articular manifestations - Severe, erosive joint disease ### Pathophysiology Rheumatoid vasculitis is an immune complex-mediated small-vessel vasculitis characterized by: 1. Deposition of immune complexes (IgG-IgM-RF complexes) in vessel walls 2. Activation of complement cascade 3. Neutrophilic infiltration and fibrinoid necrosis 4. Predominantly affects small arteries, arterioles, and capillaries ### Clinical Manifestations | Clinical Feature | Frequency | Mechanism | | --- | --- | --- | | Palpable purpura (lower extremities) | Most common | Small-vessel vasculitis of skin | | Glomerulonephritis (IgA or immune complex) | Common | Renal small-vessel involvement | | Digital ulcers and gangrene | Common | Peripheral ischemia | | Mononeuritis multiplex | Moderate | Peripheral nerve vasculitis | | Mesenteric ischemia | Less common | Mesenteric vessel involvement | | Cardiac involvement (pericarditis, myocarditis) | Rare | Systemic inflammation | **Clinical Pearl:** The presence of palpable purpura and glomerulonephritis in a patient with long-standing RA is highly suggestive of rheumatoid vasculitis. Skin biopsy typically shows leukocytoclastic vasculitis. ### Diagnostic Approach ```mermaid flowchart TD A[Patient with RA + new systemic symptoms]:::outcome --> B{Palpable purpura or organ involvement?}:::decision B -->|Yes| C[Check RF, anti-CCP, complement levels]:::action C --> D[Skin or affected organ biopsy]:::action D --> E{Vasculitis confirmed?}:::decision E -->|Yes| F[Rheumatoid vasculitis diagnosis]:::outcome E -->|No| G[Consider other vasculitides]:::action B -->|No| H[Reassess for other causes]:::action ``` **Mnemonic: RAVE** — **R**heumatoid **A**rthritis **V**asculitis **E**xtra-articular manifestations (palpable purpura, neuropathy, glomerulonephritis). ### Why Rheumatoid Vasculitis is Most Common in RA - Direct immune complex deposition in vessels - Chronic antigenic stimulation in RA - Loss of immune tolerance - Genetic predisposition (HLA associations) ### Management Principles 1. **Immunosuppression:** Corticosteroids + DMARDs (methotrexate, biologics) 2. **Biologic therapy:** TNF inhibitors, rituximab (often effective) 3. **Supportive care:** Treat underlying RA aggressively **Warning:** Do not confuse with vasculitis secondary to anti-TNF therapy (which presents differently and is less common in untreated RA). [cite:Harrison 21e Ch 378; Robbins 10e Ch 11]