Vasculitis for USMLE Step 1 & COMLEX-USA Level 1

• Definition: Vasculitis is the inflammation of blood vessels, which leads to vessel wall damage, narrowing, or occlusion, affecting blood flow to tissues and organs.

• Classification:
• Large vessel vasculitis: Involves large arteries (e.g., giant cell arteritis, Takayasu arteritis).
• Medium vessel vasculitis: Involves medium-sized arteries (e.g., polyarteritis nodosa, Kawasaki disease).
• Small vessel vasculitis: Involves small vessels like capillaries, arterioles, and venules (e.g., granulomatosis with polyangiitis, microscopic polyangiitis, Henoch-Schönlein purpura).

• Etiology:
• Idiopathic in most cases, but can also be secondary to infections, autoimmune diseases, drug reactions, or malignancies.

• Immune System Activation:
• Vasculitis can result from immune complex deposition (e.g., Henoch-Schönlein purpura) or direct T-cell or antibody-mediated vessel damage (e.g., ANCA-associated vasculitis).

• End-organ Damage:
• Inflammation leads to vessel wall destruction, ischemia, and potential organ dysfunction (e.g., renal failure in small vessel vasculitis).

• General Symptoms:
• Systemic symptoms include fever, weight loss, fatigue, and malaise.
• Symptoms vary based on the type of vasculitis and the organs affected.

• Large Vessel Vasculitis:
• Giant cell arteritis: Temporal headache, jaw claudication, vision loss.
• Takayasu arteritis: Weak pulses, blood pressure discrepancies between limbs, limb claudication.

• Medium Vessel Vasculitis:
• Polyarteritis nodosa (PAN): Hypertension, abdominal pain, kidney involvement, mononeuritis multiplex.
• Kawasaki disease: Fever, mucocutaneous inflammation, coronary artery aneurysms.

• Small Vessel Vasculitis:
• Granulomatosis with polyangiitis (GPA): Sinusitis, lung nodules, glomerulonephritis.
• Microscopic polyangiitis (MPA): Pulmonary hemorrhage, renal failure.
• Henoch-Schönlein purpura (HSP): Palpable purpura, abdominal pain, arthritis, renal involvement.

• Laboratory Tests:
• Elevated ESR and CRP indicate systemic inflammation.
• Autoantibodies: ANCA for GPA and MPA, elevated IgA for HSP.

• Imaging:
• Angiography for medium/large vessel vasculitis to detect aneurysms or stenosis.
• CT/MRI to assess structural damage or vessel abnormalities.

• Biopsy:
• Definitive diagnosis requires histological examination, particularly for small vessel vasculitis.

• Corticosteroids:
• High-dose corticosteroids are the mainstay of treatment for most forms of vasculitis.
• Gradual tapering is essential to prevent relapse.

• Immunosuppressive Therapy:
• Cyclophosphamide, methotrexate, and azathioprine for severe or refractory cases.
• Rituximab for ANCA-associated vasculitis.

• Special Treatments:
• IVIG: Administered for Kawasaki disease to prevent coronary artery aneurysms.
• Tocilizumab: Used for giant cell arteritis.

• Vasculitis is classified based on the size of the affected vessels: large, medium, or small.
• Immune system involvement is central to the pathophysiology, with immune complexes or ANCA playing a role in many types.
• Diagnosis often requires a combination of clinical features, laboratory tests (e.g., ANCA), and biopsy.
• Corticosteroids are the first-line treatment, with immunosuppressive therapy for severe cases.
• Early recognition and treatment are crucial to prevent long-term complications like organ damage or aneurysms.