Synopsis
Recognise two sentinel patterns of systemic vessel injury, localise painful axonal neuropathy, stabilise alveolar haemorrhage and rapidly progressive glomerulonephritis, and secure tissue-directed treatment before permanent organ loss.
- Vasculitic neuropathy classically begins as acute or subacute painful, asymmetric sensory or sensorimotor loss affecting separate named nerves; mononeuritis multiplex can later look confluent and symmetrical.
- Map individual movements, reflexes and sensory territories, then use nerve-conduction studies and EMG to demonstrate a multifocal axonal process and select a still-active nerve for biopsy.
- Pathologically definite vasculitic neuropathy requires vessel-wall inflammation with vascular damage; a combined targeted nerve and muscle biopsy increases information but a negative sample cannot exclude patchy disease.
- Pulmonary-renal syndrome means diffuse alveolar haemorrhage or pulmonary capillaritis with glomerulonephritis; ANCA vasculitis and anti-GBM disease are urgent causes, but lupus, cryoglobulinaemia, infection and medicines also occur.
- Haemoptysis is not required for alveolar haemorrhage. Suspect it from falling haemoglobin, hypoxaemia, diffuse new opacity and progressively bloodier bronchoalveolar lavage after infection and cardiogenic causes are considered.
- Send PR3-ANCA, MPO-ANCA and anti-GBM urgently with ANA, complement, cryoglobulins, hepatitis and cultures, but do not diagnose or exclude active vasculitis from one antibody result.
Key red flags
Hypoxaemia, increasing work of breathing, falling haemoglobin or diffuse new ground-glass or air-space opacity suggests alveolar haemorrhage even when haemoptysis is absent.
Oliguria, rapidly rising creatinine, severe hypertension, hyperkalaemia, acidosis or pulmonary oedema requires immediate nephrology and renal-replacement assessment.
Anti-GBM disease is suspected when alveolar haemorrhage accompanies rapidly progressive glomerulonephritis; treatment must begin before confirmation if waiting would cause organ loss.
New foot drop, wrist drop, asymmetric weakness, sphincter symptoms or rapidly ascending deficit requires urgent localisation and exclusion of cord, cauda equina and compressive disease.
Fever, shock, murmur, indwelling-device infection or cavitating pneumonia can mimic vasculitis; obtain cultures and deliver sepsis treatment without postponing respiratory support.
New bilateral opacity, hypoxaemia and falling haemoglobin with or without haemoptysis requires urgent capillaritis and bleeding assessment.
Creatinine rising over days to weeks with dysmorphic haematuria, casts and proteinuria indicates destructive glomerular inflammation until proved otherwise.
Investigation priorities
Grade respiratory and renal threat before aetiological results return.
Management branches
Hypoxaemia, alveolar opacity and active glomerular urine occur together.
- Admit to a monitored setting, support oxygenation and circulation and treat hyperkalaemia, acidosis, overload and infection or major bleeding immediately.
- Draw antibody, complement, viral and culture samples before exchange or immunosuppression when this does not delay organ rescue.
- Arrange CT, bronchoscopy when safe and kidney biopsy within 24 hours, coordinating respiratory, nephrology, rheumatology and critical care.
Biopsy and phenotype support organ-threatening GPA or MPA.
- Begin glucocorticoid using the reduced BSR taper or an avacopan-containing specialist plan and provide infection, bone, gastric and metabolic safeguards.
- Select intravenous pulsed cyclophosphamide or licensed-dose rituximab; prefer rituximab for relapsing disease and individualise fertility and severe-renal considerations.
- Consider plasma exchange for creatinine above 300 micromol/L after risk assessment, but do not use it routinely for pulmonary haemorrhage without severe renal disease.