Approach to Vasculitis
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Direct answer
Size the vessel before you name the syndrome: large-vessel disease is giant cell arteritis and Takayasu arteritis; medium-vessel disease is polyarteritis nodosa and Kawasaki disease; small-vessel disease divides into the ANCA-associated group (granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis) and immune-complex disease (IgA vasculitis, cryoglobulinaemic vasculitis). The clinical pattern — age, sex, organ constellation, accompanying asthma, hepatitis or upper-airway disease — plus PR3 or MPO antibodies, biopsy and angiography assembles the diagnosis. Severity, scored on the Five-Factor Scale, then sets treatment intensity: glucocorticoids alone for limited disease, with cyclophosphamide or rituximab added for organ- or life-threatening involvement.
What you must remember
- Large vessel: Takayasu arteritis — woman under 40, with the Indian subcontinent among the highest-prevalence regions, pulse deficits and limb claudication ("pulseless disease"); giant cell arteritis — woman over 50, new headache, jaw claudication, threatened vision.
- Medium vessel: polyarteritis nodosa — hepatitis B-associated, mononeuritis multiplex, testicular or mesenteric ischaemia, and it spares the lungs; treat the virus (entecavir or tenofovir) with plasmapheresis and brief steroids.
- ANCA map: PR3 (cANCA) with granulomatosis with polyangiitis — saddle-nose deformity, septal perforation, refractory otitis, haemoptysis; MPO (pANCA) with microscopic polyangiitis — the renal-pulmonary syndrome with pauci-immune crescentic glomerulonephritis.
- EGPA: adult asthma for years, eosinophils above 10 per cent, ANCA positive in about 40 per cent — ANCA-positive patients get neuropathy and nephritis, ANCA-negative get cardiac and pulmonary disease.
- Mononeuritis multiplex is small-to-medium vessel disease until excluded: check cryoglobulins (warm transport), hepatitis C and B, ANCA and complement.
- Five-Factor Score (2009): age over 65, renal impairment, gastrointestinal, cardiovascular and central nervous involvement — one point or more earns cyclophosphamide or rituximab alongside steroids.
- IgA vasculitis replaced "Henoch-Schönlein purpura" in the 2012 Chapel Hill nomenclature — children with palpable purpura, abdominal pain (intussusception) and glomerulonephritis.
- Avacopan, a C5a receptor blocker, is a validated steroid-sparing addition for ANCA-associated vasculitis.
How to work through a suspected vasculitis
Begin at the bedside, not with the panel. Palpate every pulse, compare blood pressure between arms, listen for bruits and test sensation — a wrist drop or foot drop is mononeuritis multiplex and reshapes the differential immediately. Then the red-flag urinalysis: dipstick haematuria with proteinuria in a systemically ill patient is crescentic nephritis until excluded, and it fast-tracks everything downstream.
Then laboratories in the right order: ANCA by ELISA reporting PR3 and MPO separately (immunofluorescence alone is insufficient), hepatitis B and C serology, cryoglobulins drawn warm and delivered warm, complement levels — low in cryoglobulinaemic and immune-complex disease, normal in ANCA-associated vasculitis — and an absolute eosinophil count. Then tissue: skin, sural nerve, kidney or temporal artery, taken before or within days of the first steroid dose. Then imaging where medium and large vessels are suspect: CT or MR angiography showing beading and microaneurysms in polyarteritis nodosa, and long-segment stenoses in Takayasu, which can involve pulmonary arteries too. Finally, treatment proportionate to the Five-Factor Score — and in hepatitis-B-associated polyarteritis the sequence matters: antiviral first, plasmapheresis next, with only brief steroid cover, because sustained immunosuppression keeps the virus replicating.
The classic trap
Calling polyarteritis nodosa an "ANCA-positive vasculitis". By Chapel Hill definition, PAN is not ANCA-associated; if PR3 or MPO comes back positive, the diagnosis is microscopic polyangiitis or GPA, and the treatment pathway shifts entirely, because hepatitis-B PAN is managed antiviral-first. The second trap is the cryoglobulin sample left to clot in a cold tube — a false negative closes the mind to hepatitis C. And in the young Indian woman with absent upper-limb pulses, atherosclerosis is not on the list, Takayasu is, and a CT angiogram of the aorta belongs in the same admission.
Frequently asked questions
How is the 2012 Chapel Hill classification organised?
By dominant vessel size — large, medium, small (ANCA-associated versus immune complex) — with a variable-vessel category that includes Behçet disease.
Which vasculitis is associated with hepatitis B?
Polyarteritis nodosa, classically; treatment is antiviral therapy with plasmapheresis and only brief glucocorticoid exposure.
What does PR3 versus MPO positivity suggest?
PR3 associates with granulomatosis with polyangiitis (cANCA); MPO with microscopic polyangiitis and EGPA (pANCA).
Which score decides escalation to cyclophosphamide or rituximab?
The Five-Factor Score — age above 65, or renal, gastrointestinal, cardiac or central nervous system involvement.
Why must cryoglobulins be sent in a warm tube?
They precipitate at cold temperatures, so a sample that cools or clots before separation is falsely reported as negative.