ANCA-associated Small Vessel Vasculitis

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Granulomatosis with polyangiitis (GPA)

  • Granulomatous inflammation affecting small and medium sized vessels in the upper and lower respiratory tract, eyes and/or kidneys (necrotising glomerulonephritis common)

Aetiology

  • More common in northern Europeans
  • Slightly higher incidence in males (1.5:1)
  • Typically age 35-55 years

Clinical presentation

  • Constitutional symptoms and arthralgia common
  • ENT features: sinusitis, nasal crushing, epistaxis, mouth ulcers, sensorineural deafness, otitis media, 'saddle nose' (due to cartilage damage from ischaemia), subglottic inflammation
  • Respiratory features: cough, haemoptysis, pulmonary infiltrates, diffuse alveolar haemorrhage, cavitating nodules on CXR
  • Occular features: conjunctivitis, episcleritis, uveitis, optic nerve vasculitis, retinal artery occlusion, proptosis
  • Cutaneous features: palpable purpura, cutanous ulcers
  • Renal: necrotising glomerulonephritis
  • Nervous system: mononeuritis multiplex, sensorimotor polyneuropathy, cranial nerve palsies

Eosinophilic granulomatosis with polyangiitis (EPGA)

  • Eosinophilic granulomatous inflammation affecting small and medium sized vessels most commonly in the respiratory tract and skin, but can also affect the renal, cardiovascular, gastrointestinal, central and peripheral nervous system

Clinical presentation

  • Many features similar to GPA, main difference is late onset asthma, high eosinophil count and ANCA specificity

Microscopic polyangiitis

  • Necrotising vasculitis of small vessels with few immune deposits, typically with pulmonary, renal and skin involvement

Clinical presentation

  • Necrotising glomerulonephritis very common - occurs in up to 90% of patients

Investigations

Bloods

  • ESR, PV and CRP raised
  • Anaemia common in chronic disease
  • U+E for renal involvement
  • Complement is consumed during active disease - C3/C4 may fall

Immunoflorescence

  • Anti-neutrophil cytoplasmic antibodies (ANCAs): auto-antibodies against antigens in the cytoplasm of neutrophil granulocytes
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  • ANCA, anti-PR3 and anti-MPO levels can vary with disease activity
  • ANCA is negative in a proportion of all these conditions so it cannot be relied upon to confirm the diagnosis

Biopsy

  • Of affected area to confirm

Management

  • Depends on level of disease involvement
  • Most cases require treatment with IV steroids and cyclophosphamide due to their aggressive disease course
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