Microscopic Polyangiitis

Question 1

pathogenesis

Answer 1

Necrotising vasculitis with few immune deposits. No granuloma!!!Necrotising glomerulonephritis very common – 90% of patients

Question 2

investigations

Answer 2

ESR, PV, CRP raisedanaemia of chronic diseaseU&E for renal involvementurinalysisCXRbiopsy of affected area – skin, kidneyimmunology: ANCA

Question 3

how is it classified?

Answer 3

Localized – Upper/Lower respiratory tract disease without any other systemic involvement or constitutional symptomsEarly systemic -any, without organ or life threatening Generalized – renal (creatinine < 500) or other organ threateningSystemic – renal (creatinine > 500) or other vital organ failureRefractory – progressive disease unresponsive steroids + cyclo

Question 4

how is it managed?

Answer 4

Localized/early systemic – Methotrexate + steroids (?Azathioprine + steroids)Generalised/systemic o Cyclophosphamide + steroids (1st line)o Rituximab + steroids (alternative)o plasma exchange if creatinine > 500o Followed by azathioprine with alternatives being methotrexate. mycophenolate mofetil or leflunomideRefractory – IV immunoglobulins, Rituximab