Vasculitis Classification: Large, Medium, and Small Vessel Disease

Vasculitis encompasses a heterogeneous group of systemic inflammatory disorders characterized by inflammation and necrosis of blood vessel walls. The Chapel Hill Consensus Conference (CHCC) 2012 classification system organizes vasculitides by primary vessel size involved, providing a framework for diagnosis and management.

[HIGH_YIELD] The CHCC classification divides vasculitis into three main categories:

Large Vessel Vasculitis (LVV):

• Giant Cell Arteritis (GCA) - granulomatous arteritis of aorta and major branches
• Takayasu Arteritis (TAK) - granulomatous arteritis affecting aorta and primary branches

Medium Vessel Vasculitis (MVV):

• Polyarteritis Nodosa (PAN) - necrotizing arteritis of medium arteries
• Kawasaki Disease (KD) - arteritis affecting medium and small arteries

Small Vessel Vasculitis (SVV):

• ANCA-Associated Vasculitis (AAV):
  • Microscopic Polyangiitis (MPA)
  • Granulomatosis with Polyangiitis (GPA)
  • Eosinophilic Granulomatosis with Polyangiitis (EGPA)
• Immune Complex SVV:
  • Anti-GBM disease
  • Cryoglobulinemic vasculitis
  • IgA vasculitis (Henoch-Schönlein)
  • Hypocomplementemic urticarial vasculitis

[KEY_CONCEPT] Vessel size overlap frequently occurs, with many vasculitides affecting multiple vessel calibers simultaneously. The classification reflects the predominant vessel size involved rather than exclusive involvement.

Epidemiology varies significantly:

• GCA: Most common primary vasculitis in adults >50 years (incidence 15-25/100,000)
• TAK: Young women <40 years, higher prevalence in Asia
• ANCA-associated vasculitis: Incidence 10-20/million annually, peak age 65-75 years

[CLINICAL_PEARL] Primary vasculitis occurs without identifiable underlying cause, while secondary vasculitis results from infections, malignancy, or drugs. This distinction is crucial for treatment selection and prognosis.

Clinical manifestations of vasculitis depend on vessel size, location, and degree of inflammation. Constitutional symptoms (fever, weight loss, fatigue, myalgias) occur in >90% of active systemic vasculitis cases.

[HIGH_YIELD] Large Vessel Vasculitis Clinical Features:

Giant Cell Arteritis:

• Cranial symptoms: New headache (90%), jaw claudication (65%), scalp tenderness
• Visual symptoms: Amaurosis fugax, diplopia, permanent vision loss (15-20%)
• Polymyalgia rheumatica symptoms in 40-60%
• Temporal artery abnormalities: tenderness, decreased pulsation, nodularity

Takayasu Arteritis:

• Vascular claudication: Upper extremity (96%), lower extremity (84%)
• Blood pressure discrepancies >10 mmHg between arms
• Arterial bruits over carotid, subclavian, aorta
• Renovascular hypertension from renal artery stenosis

[HIGH_YIELD] Medium Vessel Vasculitis Clinical Features:

Polyarteritis Nodosa:

• Cutaneous: Livedo reticularis (50%), subcutaneous nodules, ulcers
• Neurologic: Mononeuritis multiplex (70%), peripheral neuropathy
• Renal: Hypertension, reduced GFR (glomerulonephritis rare)
• Gastrointestinal: Abdominal pain, bleeding, bowel ischemia

[HIGH_YIELD] Small Vessel Vasculitis Clinical Features:

[CLINICAL_PEARL] Pulmonary-renal syndrome (rapid progressive glomerulonephritis + pulmonary hemorrhage) is the classic presentation of MPA and severe GPA, representing a medical emergency requiring immediate treatment.

Red flag symptoms requiring urgent evaluation:

• Sudden vision loss (GCA)
• Hemoptysis with rapidly declining renal function (AAV)
• New neurologic deficits with systemic symptoms
• Severe hypertension with vascular claudication (TAK)

Diagnosis of vasculitis requires integration of clinical features, laboratory studies, imaging, and histopathology. No single test is diagnostic, and early recognition is crucial to prevent irreversible organ damage.

[HIGH_YIELD] Laboratory Studies by Vessel Size:

Large Vessel Vasculitis:

• ESR/CRP: Markedly elevated (ESR often >100 mm/hr in GCA)
• Complete blood count: Normocytic anemia, thrombocytosis
• ANCA: Typically negative

Medium/Small Vessel Vasculitis:

• ANCA testing:
  • c-ANCA/PR3-ANCA: GPA (95% generalized, 65% limited)
  • p-ANCA/MPO-ANCA: MPA (70%), EGPA (40%)
• Complement: Normal in ANCA-associated, low in immune complex disease
• Urinalysis: Active urinary sediment (RBC casts, proteinuria)

[KEY_CONCEPT] ACR/EULAR 2022 Classification Criteria for GPA:

GPA Classification Algorithm:

1. Bloody nasal discharge OR saddle nose deformity → +3 points
2. Cartilaginous involvement (ear OR nose) → +2 points
3. Conductive/sensorineural hearing loss → +1 point
4. Laryngo-tracheo-bronchial stenosis → +2 points
5. Pulmonary nodules on imaging → +2 points
6. PR3-ANCA positive OR c-ANCA positive → +5 points
7. Granulomatous inflammation on biopsy → +2 points

Score ≥5 points = GPA classification Sensitivity: 93%, Specificity: 94%

Imaging Studies:

Large Vessel:

• CT/MR angiography: Wall thickening, stenosis, aneurysms
• PET-CT: Arterial FDG uptake in active disease
• Temporal artery ultrasound: Halo sign (hypoechoic wall thickening)

Small/Medium Vessel:

• High-resolution CT chest: Pulmonary nodules, cavitation, infiltrates
• Conventional angiography: Microaneurysms, stenosis (PAN)

[CLINICAL_PEARL] Tissue biopsy remains the gold standard for definitive diagnosis when accessible. Temporal artery biopsy should be performed within 1-2 weeks of steroid initiation in suspected GCA, as histologic changes persist despite treatment.

Diagnostic Criteria Summary:

[HIGH_YIELD] Differential diagnosis includes infections (endocarditis, tuberculosis), malignancy (lymphoma), and other autoimmune diseases (SLE, antiphospholipid syndrome).

Vasculitis treatment follows a two-phase approach: induction of remission followed by maintenance therapy. Treatment intensity correlates with disease severity and organ involvement.

[HIGH_YIELD] Treatment Algorithm for ANCA-Associated Vasculitis:

AAV Treatment Decision Tree:

1. Assess Disease Severity: ├─ Life-threatening (GN, alveolar hemorrhage, CNS): Severe ├─ Constitutional symptoms + organ involvement: Generalized
   └─ Limited to upper respiratory tract: Limited

2. Induction Therapy (3-6 months): ├─ Severe/Generalized: │ ├─ Cyclophosphamide 2mg/kg/day OR │ ├─ Rituximab 375mg/m²/week x4 OR 1000mg x2 │ └─ + Corticosteroids 1mg/kg/day (max 80mg) └─ Limited: └─ Methotrexate 20-25mg/week + Corticosteroids

3. Maintenance Therapy (18-24 months): ├─ Azathioprine 2mg/kg/day OR ├─ Methotrexate 20-25mg/week OR
   └─ Rituximab 500mg q6months x4 doses

4. Corticosteroid Taper: └─ Reduce by 10mg/week to 20mg, then 2.5mg/week to 10mg, then 1mg/month to discontinuation by 4-6 months

[KEY_CONCEPT] Large Vessel Vasculitis Treatment:

Giant Cell Arteritis:

• High-dose corticosteroids: Prednisolone 1mg/kg/day (40-60mg)
• Vision-threatening disease: IV methylprednisolone 1000mg x3 days
• Steroid-sparing agents: Methotrexate 15-25mg/week, tocilizumab 162mg weekly
• Treatment duration: 12-24 months minimum

Takayasu Arteritis:

• Active inflammation: Prednisolone 1mg/kg/day
• Refractory disease: Methotrexate, azathioprine, or biologics (TNF-α inhibitors)
• Vascular interventions: Bypass surgery or angioplasty during inactive disease

[HIGH_YIELD] Evidence-Based Treatment Considerations:

TICORA Study Findings:

• Tight control strategy with regular ANCA monitoring improved outcomes
• Structured assessment every 3 months reduced relapse rates
• Early intervention for rising ANCA titers prevented organ damage

BeSt Study Insights:

• Early aggressive treatment improved long-term outcomes
• Combination therapy more effective than monotherapy in severe disease
• Biomarker-guided therapy superior to clinical assessment alone

[CLINICAL_PEARL] Pneumocystis prophylaxis (trimethoprim-sulfamethoxazole) is mandatory for patients receiving cyclophosphamide plus corticosteroids.

Medium Vessel Vasculitis Treatment:

• PAN: Cyclophosphamide + corticosteroids for severe disease, methotrexate for limited disease
• Hepatitis B-associated PAN: Antiviral therapy + corticosteroids + plasma exchange

Monitoring Parameters:

• Disease activity: Clinical assessment, inflammatory markers, ANCA titers
• Treatment toxicity: CBC, creatinine, liver function, bone density
• Relapse surveillance: ANCA rise often precedes clinical relapse by 2-6 months

Refractory Disease Options:

• Rituximab: Effective for ANCA-associated vasculitis
• Plasma exchange: Severe pulmonary-renal syndrome, anti-GBM disease
• Tocilizumab: Giant cell arteritis, Takayasu arteritis
• Mepolizumab: Eosinophilic granulomatosis with polyangiitis

Vasculitis complications arise from both active inflammatory disease and treatment-related toxicity. Early recognition and aggressive management are crucial for preventing irreversible organ damage.

[HIGH_YIELD] Acute Life-Threatening Complications:

Cardiovascular:

• Acute coronary syndrome: Coronary arteritis (Kawasaki disease, GCA)
• Aortic dissection: Large vessel vasculitis (TAK, GCA)
• Stroke: Carotid involvement, cerebral vasculitis
• Renovascular hypertension: Renal artery stenosis

Pulmonary:

• Diffuse alveolar hemorrhage: MPA, GPA (mortality 25-50%)
• Respiratory failure: Severe pulmonary involvement
• Airway stenosis: GPA (subglottic stenosis)

Renal:

• Rapidly progressive glomerulonephritis: ANCA-associated vasculitis
• End-stage renal disease: 10-15% of patients with AAV
• Dialysis requirement: 15-25% at presentation

[CLINICAL_PEARL] Permanent vision loss occurs in 15-20% of GCA patients, emphasizing the importance of immediate high-dose corticosteroid therapy for suspected cases.

Chronic Complications & Disease Damage:

Treatment-Related Complications:

Cyclophosphamide Toxicity:

• Immediate: Bone marrow suppression, infection, nausea
• Long-term: Malignancy (bladder cancer, lymphoma), infertility, premature menopause
• Cumulative dose-dependent: Total dose >36g associated with highest cancer risk

Corticosteroid Complications:

• Metabolic: Diabetes, osteoporosis, weight gain
• Cardiovascular: Hypertension, accelerated atherosclerosis
• Infectious: Increased susceptibility, atypical presentations

[HIGH_YIELD] Long-term Prognosis:

5-year Survival Rates:

• Treated GCA: >95%
• ANCA-associated vasculitis: 75-85%
• Untreated severe vasculitis: <10%

Relapse Rates:

• GPA: 50-60% within 5 years
• MPA: 30-40% within 5 years
• EGPA: 25-35% within 5 years

[KEY_CONCEPT] Damage accumulation occurs in 60-80% of vasculitis patients over time, emphasizing the importance of achieving early remission while minimizing treatment toxicity.

Quality of Life Impact:

• Chronic fatigue: Persistent in 50-70% despite remission
• Depression/anxiety: Common due to chronic disease burden
• Employment disability: 40-60% unable to work full-time

Prevention Strategies:

• Infection prophylaxis: Pneumocystis, vaccination updates
• Bone health: Calcium, vitamin D, bisphosphonates
• Cardiovascular risk: Statin therapy, blood pressure control
• Cancer surveillance: Regular screening based on treatment history

[CLINICAL_PEARL] Pregnancy planning requires preconception counseling, medication adjustment, and multidisciplinary care. Cyclophosphamide and methotrexate are contraindicated; azathioprine and corticosteroids are generally safe.