USMLE/COMLEX 3 - Large Vessel Vasculitis

Here are key facts for USMLE Step 3 & COMLEX-USA Level 3 from the Large Vessel Vasculitis tutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links.

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1. Giant Cell Arteritis (GCA) is a medical emergency due to the risk of permanent vision loss. 2. GCA typically affects women >50 years old, especially of Northern European descent. 3. Classic symptoms of GCA:

• New-onset headache (especially temporal)
• Jaw claudication
• Visual changes (amaurosis fugax, blurred vision)
• Scalp tenderness

4. High-dose corticosteroids (prednisone 40–60 mg daily) must be started immediately upon suspicion; do not delay for biopsy. 5. For vision-threatening symptoms, initiate IV methylprednisolone (e.g., 1g daily x 3 days) before oral transition. 6. Confirm diagnosis with temporal artery biopsy, but treatment should begin first. 7. GCA is associated with polymyalgia rheumatica in about 50% of cases (proximal muscle pain and stiffness, rapid response to low-dose steroids). 8. Key labs: Elevated ESR (>50 mm/hr) and elevated CRP support the diagnosis. 9. Takayasu Arteritis affects young women <40, typically of Asian descent. 10. Classic symptoms of Takayasu include:

• Absent pulses in upper extremities
• Asymmetric blood pressures (>10 mmHg difference between arms)
• Arm or leg claudication
• Carotid/subclavian bruits

11. Diagnosis of Takayasu arteritis is made with CT angiography or MR angiography, showing stenosis, occlusion, or aneurysmal changes. 12. Both conditions are primarily treated with systemic corticosteroids initially.

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1. Both GCA and Takayasu arteritis are granulomatous large vessel vasculitides. 2. Histologic features of GCA include:

• Multinucleated giant cells
• Chronic inflammatory infiltrates
• Destruction of internal elastic lamina
• Intimal thickening causing luminal narrowing

3. Takayasu pathogenesis involves chronic vessel wall inflammation, leading to fibrosis, stenosis, and ischemia. 4. GCA primarily affects branches of the external carotid artery (e.g., temporal, ophthalmic), whereas Takayasu affects the aortic arch and its branches. 5. Temporal artery biopsy has patchy involvement; a negative result does not completely exclude GCA. 6. For Takayasu, steroids are the first-line treatment, but refractory cases may require methotrexate or azathioprine. 7. Secondary hypertension in Takayasu is commonly due to renal artery stenosis. 8. Regular monitoring of ESR/CRP is important to gauge treatment response and detect relapses. 9. Chronic steroid therapy necessitates bone health management:

• Calcium and vitamin D supplementation
• Bisphosphonates for osteoporosis prevention

10. Low-dose aspirin may be added to prevent ischemic complications in both diseases if there is significant vascular involvement.

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1. In GCA with visual involvement, hospital admission for IV steroids and urgent ophthalmology consultation is warranted. 2. After initial high-dose therapy, taper steroids gradually based on clinical improvement and normalization of ESR/CRP. 3. Tocilizumab (IL-6 receptor antagonist) is an option for GCA patients who cannot tolerate long-term steroids or have frequent relapses. 4. Annual surveillance imaging (CT/MRA) for Takayasu patients is recommended to monitor for progression or recurrence. 5. Watch for complications such as:

• Aortic aneurysm or aortic regurgitation (both diseases)
• Stroke (especially in GCA due to carotid involvement)
• Myocardial ischemia or limb ischemia (especially in Takayasu)

6. Educate patients about early signs of relapse: new claudication, visual symptoms, or constitutional symptoms. 7. For GCA, re-evaluate for PMR symptoms during follow-up, as patients may require lower-dose steroid treatment tailored to PMR activity. 8. Immunosuppressive agents like methotrexate or azathioprine may help in steroid-sparing regimens for both conditions.