Overview
Clinical Pattern and Disease Mechanism
Eosinophilic granulomatosis with polyangiitis (EGPA), formerly called Churg Strauss syndrome, is an eosinophil associated necrotizing vasculitis of small and medium vessels.
Eosinophilic granulomatosis with polyangiitis (EGPA), formerly called Churg-Strauss syndrome, is an eosinophil-associated necrotizing vasculitis of small and medium vessels. The characteristic pattern is not simply “asthma plus a high eosinophil count.” It is adult-onset asthma or obstructive airway disease combined with chronic rhinosinusitis, often nasal polyps, blood or tissue eosinophilia, and evidence of injury in organs such as the lungs, peripheral nerves, skin, heart, gastrointestinal tract, kidneys, or central nervous system. The disease may evolve through an airway-predominant period, an eosinophilic tissue-infiltration period, and a vasculitic period, but these phases can overlap or appear in a different order. A patient whose asthma suddenly becomes accompanied by foot drop, palpable purpura, hematuria, or unexplained cardiac symptoms has a systemic inflammatory disorder until proven otherwise; asthma alone does not account for those findings. Eosinophils are not passive bystanders. Interleukin-5 (IL-5) promotes their growth, differentiation, recruitment, activation, and survival. Activated eosinophils release inflammatory mediators that injure tissue, while vessel-wall inflammation and necrosis impair blood flow. This combination explains why one patient may have fleeting pulmonary infiltrates and another may develop mononeuritis multiplex, myocarditis,...