features

Last reviewed 01/2018

Microscopic polyangiitis is:

• uncommon with an annual incidence depending on geographic location (varying from 2.7 to 11.6 cases per million)
• most frequent in the elderly but has a wide age range with men being affected more often than women

The clinical manifestations are varied because of the many potential sites for pathology.

The most usual presentation is with renal involvement, which may be associated with haemoptysis. It is a cause of 'pulmonary-renal syndrome'.

• pulmonary disease is less common in microscopic polyangiitis than in Wegener's granulomatosis but 30% of patients will have pulmonary haemorrhage

renal disease

• characterized by necrotizing small vessel vasculitis associated with no significant immune deposits (pauci-immune)
  • can range from an active urinary sediment to rapidly progressive glomerulonephritis with severe damage
• renal involvement in microscopic polyangiitis is invariable

Hypertension occurs in 30% of patients with microscopic polyangiiitis

other organs - ocular involvement is common and may present as conjunctivitis, scleritis or uveitis

• non-erosive arthritis occurs in up to 28% of patients
• skin disease may manifest as palpable purpura, ulcers and subcutaneous nodules - skin manifestations occur in up to 50% of patients
• involvement of the heart (pericarditis, coronary arteritis), nervous system (mononeuritis multiplex, peripheral neuropathy) and gastrointestinal tract (haemorrhagic ulceration, bowel perforation)
  • mononeuritis multiplex as in Wegener'is uncommon (<=20%), and ocular and nasopharyngeal symptoms are less common than in Wegener's (<30%) (2)

   

Reference:

• (1) Davies DG. Small vessel vasculitis. Cardiovascular Pathology 2005;14 (6): 335-346.
• (2) ARC Autumn 2012. Topical Reviews - ANCA-associated vasculitis; 1:1-12.