Churg–Strauss syndrome (
CSS, also known as
eosinophilic granulomatosis with polyangiitis [
EGPA] or
allergic granulomatosis) is an
autoimmune condition that causes
inflammation of small and medium-sized blood vessels (
vasculitis) in persons with a history of airway allergic hypersensitivity (
atopy). It usually manifests in three stages. The early (
prodromal) stage is marked by airway inflammation; almost all patients experience
asthma and/or
allergic rhinitis. The second stage is characterized by abnormally high numbers of eosinophils (
hypereosinophilia), which causes tissue damage, most commonly to the
lungs and the
digestive tract. The third stage consists of vasculitis, which can eventually lead to
cell death and can be life-threatening.