Microscopic polyangiitis Flashcards
Microscopic polyangiitis
- Most common cause of pulmonary-renal syndrome causing both _________ and _________
- A/w ____________
- Tendency to affect ________________ (unlike polyarteritis nodosa which causes only arterial lesions)
- Middle-aged to elderly, mean age 60 years old, male = female
- Some associations with _____________ use for treatment of hyperthyroidism, silica and solvent exposure
- Clinical presentation tends to be shorter compared to GPA (granulomatosis w polyangiitis)
- Can be a feature of immune disorders eg Henoch-Schonlein purpura, essential mixed cryoglobulinaemia, connective tissue disorders
alveolar haemorrhage and RPGN (renal biopsy may show crescentic glomeruli);
p-ANCA (MPO-ANCA);
both arteries and veins;
propylthiouracil (PTU)
What are the clinical features of microscopic polyangiitis?
- Common complaints and signs of GPA and MPA include fatigue, fever, weight loss, arthralgia, rhinosinusitis, cough, dyspnoea, urinary abnormalities (w or wo renal insufficiency, purpura and neurologic dysfunction
- Tracheal and pulmonary disease
- Renal manifestations
- Cutaneous manifestations
- Ophthalmic and orbital manifestations
What are the investigations for microscopic polyangiitis?
ESR/CRP – typically dramatic elevations, correlates well with disease activity
UFEME – haematuria, RBC cell casts, proteinuria
FBC – NCNC anaemia, mild-moderate leukocytosis, moderate-pronounced thrombocytosis
Electrolytes – hyperkalaemia in severe renal dysfunction
LFTs – usually normal. AST/ALT >1000 mg/dL if hepatic involvement
Serology:
- ANA – negative
- ANCA – positive usually p-ANCA pattern
- RF – can be positive in 40-50% of patients
- C3, C4 – normal
- Anti-GBM – can be positive
Tissue biopsies
- Renal biopsy: IMF staining for “pauci-immune” nature of renal involvement
- Skin biopsy: demonstrate involvement of medium-sized vessels, therefore excluding cutaneous vasculitis limited to small-vessel disease (eg hypersensitivity vasculitis, Henoch-Schonlein purpura)
- Lung biopsy: excludes infections, malignancies etc.
What is the management of Microscopic polyangiitis?
Induction of remission
- Combination therapy: cytotoxic agent + glucocorticoid
- Cytotoxic agents: rituximab (1st choice), cyclophosphamide (2nd choice). Rituximab has a better long-term side effect profile
- Dosing: 3-day IV pulse methyprednisolone, followed by 2mg/kg/d cyclophosphamide (normal renal function) + 1mg/kg/d prednisolone for 3-6 months
- Administration: cyclophosphamide can be given IV or oral
Maintenance
- Replace cyclophosphamide with azathioprine (up to 2mg/kg/d) or methotrexate (20-25mg/wk) for 1 year upon achieving remission
- For renal damage: blood pressure control, ACEi, salt restriction
Prophylaxis against PCP: daily dose single-strength Bactrim or 100mg/d dapsone or 1500mg/d atovaquone
What are the similarities of MPA vs WG?
- Both presents with preceding constitutional symptoms of fever, fatigue, LOW
- Both are very similar diseases, characteristically involving the respi tract & kidneys
- Both can cause devastating pulmonary-renal syndrome
- Both are ANCA +ve, Necrotizing Vasculitis
- Renal histo for both shows: focal necrotizing, pauci-immune glomerulonephritis
What are 4 differences between MP and WG?
Microscopic Polyangiitis
- C-ANCA
- No granuloma on histology
- Lower rates of URT involvement – nasopharynx, tracheal involvement is RARE (mainly lungs)
- Lower rates of relapse after immunosuppression
Wegener’s Granulomatosis
- P-ANCA
- Granulomatous, Neutrophil Predominent
- Higher rates of URT involvement
- Higher rates of relapse after immunosuppression
