Small vessel vasculitides (classification, pathomechanism, symptoms, treatment)

1. Big picture

Small vessel vasculitides affect capillaries, venules, arterioles, and small arteries. Clinically, this means they commonly present with:

• Palpable purpura — skin small vessels
• Glomerulonephritis — renal capillaries
• Pulmonary capillaritis / alveolar hemorrhage — lung capillaries
• Mononeuritis multiplex — vasa nervorum
• ENT disease, asthma, eosinophilia, abdominal pain, arthralgia depending on subtype

The exam logic is:

Purpura + renal urine abnormalities ± lung symptoms = think small vessel vasculitis until proven otherwise.

The most important group for internal medicine is ANCA-associated vasculitis (AAV): granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Modern EULAR recommendations state that suspected AAV should be evaluated with ANCA testing and biopsy when possible, and organ-threatening disease should be treated with high-dose glucocorticoids plus rituximab or cyclophosphamide. ([PubMed][1])

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