Polyarteritis Nodosa / GPA - Orthopaedic Relevance
- The systemic VASCULITIDES are rare, multi-organ INFLAMMATORY disorders of BLOOD VESSELS, classified by the SIZE of the vessel involved (Chapel Hill): LARGE-vessel (giant-cell/temporal arteritis, Takayasu), MEDIUM-vessel (POLYARTERITIS NODOSA, Kawasaki), and SMALL-vessel (the ANCA-associated vasculitides - GPA, microscopic polyangiitis, EGPA - and immune-complex types) - examples such as Takayasu (large), polyarteritis nodosa (medium) and lupus/drug-induced (small) each show distinct imaging features.
- POLYARTERITIS NODOSA (PAN) is a necrotising MEDIUM-vessel arteritis that forms ANEURYSMS (a beaded/'rosary' appearance on angiography) and causes skin lesions (nodules, livedo reticularis, ulcers), MONONEURITIS MULTIPLEX, renal, gastrointestinal and limb ISCHAEMIA; it characteristically SPARES the lungs and is usually ANCA-NEGATIVE (and may be hepatitis-B-associated).
- GRANULOMATOSIS WITH POLYANGIITIS (GPA, formerly Wegener's) is a small-vessel ANCA-associated vasculitis with the classic triad of upper-airway/ENT, lung and kidney involvement (c-ANCA/anti-PR3), alongside microscopic polyangiitis (p-ANCA/anti-MPO) and eosinophilic GPA (asthma, eosinophilia) - these are the small-vessel diseases to recognise.
- The MUSCULOSKELETAL manifestations are common but usually non-specific: ARTHRALGIA and MYALGIA and a usually NON-EROSIVE inflammatory ARTHRITIS, plus constitutional symptoms (fever, weight loss, malaise) and raised inflammatory markers - so a vasculitis can present with limb/joint symptoms before its organ-specific features.
- The ORTHOPAEDICALLY DANGEROUS manifestations are vascular and neural: LIMB and DIGITAL ISCHAEMIA progressing to GANGRENE, and MONONEURITIS MULTIPLEX (a vasculitic neuropathy causing, for example, foot drop or wrist drop) - these can be mistaken for primary peripheral vascular disease, an entrapment neuropathy or a compartment/orthopaedic problem, and the error of treating the limb without recognising the vasculitis leads to ongoing tissue loss.
- The KEY PRINCIPLE is that recognition leads to URGENT IMMUNOSUPPRESSION, not surgery alone: systemic vasculitis is treated with CORTICOSTEROIDS plus CYCLOPHOSPHAMIDE or RITUXIMAB for induction (with maintenance immunosuppression), addressing any trigger (e.g. hepatitis B in PAN); surgical management of ischaemic tissue/gangrene or nerve palsy must occur ALONGSIDE controlling the underlying disease. Note that this is a reasoned PRINCIPLE rather than a measured finding - no study has compared surgery with versus without concurrent immunosuppression, and no amputation rate or nerve-recovery rate has been published for vasculitic limb disease.
- KNOW THE INDUCTION NUMBERS. In the RAVE trial (197 randomised patients, double-blind), remission off prednisone at 6 months was achieved by 64% on RITUXIMAB versus 53% on CYCLOPHOSPHAMIDE - non-inferior (P less than 0.001) - and rituximab was SUPERIOR in RELAPSING disease (67% versus 42%, P = 0.01), with equal efficacy in major renal disease and alveolar haemorrhage. Crucially there was NO significant difference in adverse events, so 'rituximab is safer' overstates it: choose it for relapsing disease and to avoid cyclophosphamide's gonadotoxicity.
- “Classify vasculitis by VESSEL SIZE: large (GCA/Takayasu), medium (PAN, Kawasaki), small/ANCA (GPA c-ANCA/PR3, MPA p-ANCA/MPO, EGPA). PAN = aneurysms, spares lungs, usually ANCA-negative (HBV link).
- “MSK = arthralgia/myalgia + usually NON-EROSIVE arthritis + constitutional symptoms. DANGER = digital/limb ischaemia/gangrene and MONONEURITIS MULTIPLEX (foot/wrist drop) - can mimic primary orthopaedic/vascular disease.
- “Recognition → URGENT immunosuppression (steroids + cyclophosphamide/rituximab). Surgery on ischaemic tissue/nerve must go WITH treating the vasculitis - a reasoned principle, though no study has compared surgery with versus without immunosuppression.
- “RAVE (n = 197): remission off prednisone at 6 months 64% rituximab vs 53% cyclophosphamide (non-inferior); SUPERIOR in relapsing disease 67% vs 42% (P = 0.01); NO significant difference in adverse events - so prefer rituximab for relapsing disease and fertility, not on a proven safety edge.
Classification & Key Diseases
Vessel size is the classification. The systemic vasculitides are rare, multi-organ inflammatory disorders of blood vessels, classified (Chapel Hill) by the size of the vessel involved: large, medium or small. The small-vessel group divides again into the ANCA-associated diseases and the immune-complex diseases.
- Examples
- Giant-cell (temporal) arteritis, Takayasu
- MSK / limb relevance
- Polymyalgia rheumatica overlap; limb claudication (Takayasu)
- Examples
- Polyarteritis nodosa, Kawasaki
- MSK / limb relevance
- Myalgia, mononeuritis multiplex, digital/limb ischaemia & gangrene
- Examples
- GPA, microscopic polyangiitis, EGPA
- MSK / limb relevance
- Arthralgia/arthritis, mononeuritis multiplex, digital ischaemia
Large-vessel disease. Giant-cell (temporal) arteritis presents with headache, jaw claudication and visual loss. Takayasu arteritis involves the aorta and its branches and is known as pulseless disease.
Polyarteritis nodosa. PAN is a necrotising arteritis of medium arteries that forms aneurysms, seen as beaded or "rosary" vessels on angiography. It causes skin lesions (nodules, livedo reticularis, ulcers), mononeuritis multiplex, and renal, gastrointestinal and limb ischaemia. It characteristically spares the lungs, is usually ANCA-negative, and may be hepatitis-B-associated. Kawasaki disease, in children, also sits in the medium-vessel group.
The ANCA-associated small-vessel diseases. These are the pauci-immune vasculitides:
- Granulomatosis with polyangiitis (GPA, formerly Wegener's): the triad of upper-airway/ENT, lung and kidney involvement, with c-ANCA/anti-PR3
- Microscopic polyangiitis (MPA): p-ANCA/anti-MPO
- Eosinophilic GPA (EGPA, Churg-Strauss): asthma and eosinophilia
What ANCA is. Anti-neutrophil cytoplasmic antibodies are read on immunofluorescence in two patterns. c-ANCA (cytoplasmic) targets proteinase-3 (PR3) and is found in about 90 percent of GPA; p-ANCA (perinuclear) targets myeloperoxidase (MPO) and is typical of MPA and of ANCA-positive EGPA. The pattern is confirmed by antigen-specific ELISA. The antibodies are pathogenic, activating neutrophils to damage the endothelium.
The Small-Vessel Immune-Complex Group
The immune-complex group. Small-vessel vasculitis is either ANCA-associated or immune-complex. In the immune-complex vasculitides, immunoglobulin and/or complement is deposited in the vessel wall.
IgA vasculitis (Henoch-Schonlein purpura). The commonest childhood vasculitis is an IgA1 immune-complex disease, often post-infective. It is mostly self-limiting and managed supportively. Its tetrad:
- Palpable purpura over the buttocks and legs, non-thrombocytopenic
- Arthritis or arthralgia of the knees and ankles, transient and non-deforming: the orthopaedic overlap
- Abdominal pain: colic, gastrointestinal bleeding, intussusception
- Nephritis (IgA nephropathy)
Cryoglobulinaemic vasculitis. The vasculitis of cold-precipitating immunoglobulins is strongly hepatitis-C-associated, with purpura, arthralgia, peripheral neuropathy and glomerulonephritis. Treatment is of the hepatitis C plus immunosuppression.
Orthopaedic Manifestations
The common picture. Arthralgia, myalgia and a usually non-erosive inflammatory arthritis are common but usually non-specific. They come with constitutional symptoms (fever, weight loss, malaise) and raised inflammatory markers, and may precede the organ-specific features, so a vasculitis can present with limb or joint symptoms first.
The limb-threatening picture. The orthopaedically dangerous manifestations are vascular and neural. Digital and peripheral ischaemia can progress to gangrene, and mononeuritis multiplex, a vasculitic neuropathy, can present as a foot drop or wrist drop.
Vasculitic gangrene can be mistaken for atherosclerotic peripheral vascular disease, and a vasculitic foot or wrist drop for an entrapment neuropathy or compartment syndrome. An amputation, revascularisation or nerve decompression performed without controlling the vasculitis will be undermined by ongoing inflammatory vessel disease, with further tissue loss.
Management
Recognition is the key step. Recognition rests on the systemic picture: constitutional symptoms, multi-organ involvement and raised inflammatory markers, confirmed with ANCA and other serology and with biopsy or angiography.
Urgent immunosuppression. Induction is with corticosteroids plus cyclophosphamide or rituximab, followed by maintenance immunosuppression. Any trigger is treated, such as hepatitis B in PAN.
Choosing the induction agent in ANCA-associated vasculitis. Induction there is with glucocorticoids plus rituximab (anti-CD20) or cyclophosphamide. The RAVE trial (197 patients, 9 centres, double-blind double-dummy) took remission off prednisone at 6 months as its endpoint: 64% on rituximab versus 53% on cyclophosphamide, meeting non-inferiority (P less than 0.001). Rituximab was equally effective in major renal disease and alveolar haemorrhage. In relapsing disease it was superior, 67% (34 of 51) versus 42% (21 of 50), P = 0.01, and that is the strongest reason to prefer it.
Be accurate about "safer". Uncontrolled studies had suggested rituximab was safer, but RAVE found no significant difference in adverse-event rates between the two arms. Its genuine advantages are the result in relapsing disease and the avoidance of cyclophosphamide's gonadotoxicity and bladder and malignancy risk.
Adjuncts and maintenance in ANCA-associated vasculitis. Plasma exchange is used for severe renal failure or pulmonary haemorrhage, a role narrowed by the PEXIVAS trial. Avacopan, an oral C5a-receptor inhibitor, is a glucocorticoid-sparing agent. Maintenance is with rituximab or azathioprine.
Surgery goes alongside disease control. Gangrenous tissue is debrided or amputated and nerve palsies are managed, but only with the vasculitis controlled: surgery alone, with the disease untreated, fails. That is a reasoned principle rather than a measured finding. No study has compared surgery with versus without concurrent immunosuppression, and no amputation rate or nerve-recovery rate has been published for vasculitic limb disease.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A patient presents with a foot drop and digital ischaemia, plus fever, weight loss and raised inflammatory markers. Why should you think beyond a simple nerve or vascular problem?”
Classification (vessel size)
- Large: giant-cell (temporal) arteritis, Takayasu
- Medium: polyarteritis nodosa (aneurysms, spares lungs, usually ANCA-negative, HBV link), Kawasaki
- Small/ANCA: GPA (c-ANCA/PR3), microscopic polyangiitis (p-ANCA/MPO), EGPA (asthma/eosinophilia)
MSK manifestations
- Arthralgia/myalgia + usually non-erosive arthritis
- Constitutional symptoms (fever, weight loss) + raised inflammatory markers
- May precede organ-specific features
Limb-threatening / the trap
- Digital/peripheral ischaemia → gangrene (mimics PVD)
- Mononeuritis multiplex → foot/wrist drop (mimics entrapment neuropathy)
- Don't treat the limb as primary orthopaedic/vascular disease
Management
- Recognise systemic picture; ANCA/serology, biopsy/angiography
- Urgent immunosuppression: steroids + cyclophosphamide or rituximab (treat HBV in PAN)
- RAVE (n = 197): 64% vs 53% remission off prednisone at 6 months - rituximab non-inferior
- Rituximab SUPERIOR in relapsing disease (67% vs 42%, P = 0.01); NO adverse-event difference
- Surgery for gangrene/nerve palsy alongside disease control - a principle; no trial has tested it
- Consider DADA2 in young PAN-like disease - it responds to TNF inhibition instead
Evidence & Key Studies
Imaging classification of vasculitis by vessel size (Takayasu, PAN, small-vessel)
- A NARRATIVE IMAGING REVIEW written for emergency radiology - it describes CT angiographic appearances and supplies no prevalence, outcome or treatment data of any kind.
- Systemic vasculitides are rare, multi-organ inflammatory disorders of blood vessels, classified by the size of the affected vessel.
- Examples include Takayasu arteritis (large vessels), polyarteritis nodosa (medium vessels), and lupus-associated or drug-induced vasculitis (small vessels), each with distinct imaging features on CT angiography.
- Early recognition of the imaging findings is described as crucial for diagnosis, treatment and assessing the need for surgical intervention - an expert statement rather than a measured effect of early recognition.
Rituximab versus cyclophosphamide for ANCA-associated vasculitis (the RAVE trial)
- Multicentre, randomised, double-blind, DOUBLE-DUMMY non-inferiority trial across 9 centres: 197 ANCA-positive patients with granulomatosis with polyangiitis or microscopic polyangiitis. Rituximab 375 mg/m2 weekly for 4 weeks versus cyclophosphamide 2 mg/kg/day, with glucocorticoids tapered off entirely.
- PRIMARY ENDPOINT - remission WITHOUT prednisone at 6 months: 63 of 98 (64%) on rituximab versus 52 (53%) on cyclophosphamide, meeting the non-inferiority criterion (P less than 0.001).
- SUPERIOR IN RELAPSING DISEASE: 34 of 51 (67%) versus 21 of 50 (42%), P = 0.01 - the subgroup that most justifies choosing rituximab. It was also as effective as cyclophosphamide in major renal disease and alveolar haemorrhage.
- IMPORTANT CORRECTION TO A COMMON CLAIM: although uncontrolled studies had suggested rituximab was safer, there were NO significant differences between the treatment groups in adverse-event rates. The case for rituximab rests on relapsing disease and on avoiding cyclophosphamide's gonadotoxicity, not on a demonstrated overall safety advantage.
- Limitations for an orthopaedic reader: the endpoint is remission off steroids at 6 months, not limb salvage, tissue loss or neurological recovery - no trial has measured whether immunosuppression prevents amputation or reverses vasculitic nerve palsy.
Polyarteritis-nodosa-like vasculitis in DADA2 - a medium-vessel vasculitis example
- SCOPE: a SINGLE CASE REPORT of DADA2 - a MONOGENIC autoinflammatory disease that mimics polyarteritis nodosa. It is not a study of polyarteritis nodosa itself, and supplies no frequency, outcome or comparative data.
- Deficiency of adenosine deaminase 2 is a monogenic condition whose small- and medium-vessel involvement can produce features resembling polyarteritis nodosa - worth knowing because a young patient with apparent PAN, particularly with early strokes or a family history, may have DADA2 instead.
- The reported patient had systemic inflammation (fever, weight loss, raised inflammatory markers) with organ involvement, treated successfully with corticosteroids and a TNF inhibitor.
- That treatment distinction matters: DADA2 responds to TNF INHIBITION rather than to the cyclophosphamide or rituximab used in ANCA-associated disease - so the mimic and the disease are not managed identically. A single case cannot establish how reliably this works.
The induction figures - 64% versus 53% remission off prednisone at 6 months, superiority in relapsing disease at 67% versus 42% (P = 0.01), and the absence of any significant difference in adverse events - come from the RAVE trial (DOI), 197 randomised patients. The vessel-size imaging descriptions come from Rahmatullah (DOI), a narrative imaging review, and the DADA2 mimic from Al-Ghoul (DOI), a single case report of a monogenic disease rather than of polyarteritis nodosa. The Chapel Hill vessel-size classification, the ANCA associations of GPA, MPA and EGPA, the PAN features (aneurysms, lung sparing, ANCA-negativity, hepatitis-B link), the immune-complex small-vessel group, and the mononeuritis multiplex and digital-ischaemia presentations are standard, well-established teaching.
Be honest about the page's central orthopaedic principle. That operating on a vasculitic limb without treating the underlying disease leads to ongoing tissue loss is a reasoned principle, not a measured finding: no trial or cohort has compared surgery with versus without concurrent immunosuppression, and RAVE's endpoint was remission off steroids at 6 months, not amputation, limb salvage or recovery of a vasculitic nerve palsy. There is likewise no published amputation rate for vasculitic digital gangrene, no recovery rate for mononeuritis multiplex after immunosuppression, and no evidence defining how long disease control should precede elective surgery. The principle is sound physiologically and widely taught - it simply has no number attached to it.