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 raised
anaemia of chronic disease
U&E for renal involvement
urinalysis
CXR
biopsy of affected area – skin, kidney
immunology: ANCA

Question 3

how is it classified?

Answer 3

Localized – Upper/Lower respiratory tract disease without any other systemic involvement or constitutional symptoms
Early systemic -any, without organ or life threatening
Generalized – renal (creatinine < 500) or other organ threatening
Systemic – renal (creatinine > 500) or other vital organ failure
Refractory – 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 > 500
o Followed by azathioprine with alternatives being methotrexate. mycophenolate mofetil or leflunomide
Refractory – IV immunoglobulins, Rituximab