AKT · Musculoskeletal/Vasculitis, PMR & GCAlow yield

Vasculitides

Inflammation of blood-vessel walls — classified by vessel size (small/medium/large; ANCA-associated)

Overview

A heterogeneous group of conditions defined by blood-vessel-wall inflammation, classified by vessel size: large (GCA, Takayasu), medium (polyarteritis nodosa, Kawasaki) and small (ANCA-associated — GPA, EGPA, MPA — and immune-complex, e.g. IgA vasculitis/HSP). They present with multisystem disease and constitutional symptoms; ANCA-associated vasculitis classically causes a pulmonary-renal syndrome. Many are organ- and life-threatening and need immunosuppression.

Recognise

Constitutional (fever, weight loss, malaise) + multisystem: skin (palpable purpura), renal (glomerulonephritis), lung (haemorrhage), nerve (mononeuritis multiplex), ENT
GPA (Wegener's): ENT (saddle-nose, sinusitis, epistaxis) + lung + kidney, cANCA/anti-PR3. MPA: pANCA/anti-MPO. EGPA (Churg-Strauss): asthma + eosinophilia + pANCA
Polyarteritis nodosa: medium-vessel, hepatitis B association, renal/GI/skin, spares the lungs; Takayasu: 'pulseless disease' in young women

Red flags

Pulmonary-renal syndrome (haemoptysis + AKI/active sediment) → rapidly progressive glomerulonephritis → emergency immunosuppression ± plasma exchange
Mononeuritis multiplex, gut/cardiac involvement → organ-threatening disease

Differentials & how to tell them apart

Infection / infective endocarditiscan mimic vasculitis with multisystem signs and positive ANCA occasionally — exclude

Malignancy / cholesterol emboliother causes of multisystem/constitutional disease

Connective tissue disease (SLE)different autoantibody profile, overlapping features

Investigations

ANCA (cANCA/PR3 → GPA; pANCA/MPO → MPA/EGPA); urinalysis + renal function (glomerulonephritis); inflammatory markers; eosinophils (EGPA); hepatitis B (PAN); imaging (CT chest/sinuses, angiography); tissue biopsy (skin/kidney/nerve) for definitive diagnosis.

Management

Induction with steroids + cyclophosphamide/rituximab for organ-threatening disease

1Classify by vessel size and ANCA status; assess organ involvement (urinalysis/renal function, chest imaging, nerves). Confirm with biopsy where feasible.Gate: Pulmonary-renal syndrome / rapidly progressive glomerulonephritis → emergency induction immunosuppression (steroids + cyclophosphamide or rituximab) ± plasma exchange — do not delay.
2Maintain remission with azathioprine/methotrexate/rituximab; treat cause-specific disease (antivirals for HBV-associated PAN); long-term relapse surveillance.

Induction: high-dose corticosteroids + cyclophosphamide or rituximab — for organ-threatening ANCA-associated vasculitis

Plasma exchange — for severe pulmonary haemorrhage or severe renal failure in selected cases

Maintenance: azathioprine, methotrexate or rituximab — after remission induction

Treat cause-specific disease — antivirals for hepatitis-B-associated PAN; IVIg/aspirin for Kawasaki (child_health)

Key points

Multisystem disease + constitutional symptoms + palpable purpura/glomerulonephritis = vasculitis. ANCA pattern points the way: cANCA/PR3 = GPA (ENT+lung+kidney, saddle nose); pANCA/MPO = MPA; EGPA = asthma+eosinophilia. Pulmonary-renal syndrome → emergency immunosuppression.

Monitor & prognosis

ANCA/inflammatory markers, renal function/urinalysis, immunosuppression safety, relapse.

Once frequently fatal; modern immunosuppression achieves remission in most, but relapse and treatment toxicity persist.

Source: BSR/EULAR vasculitis; cross-ref child_health (HSP, Kawasaki)