Churg-Strauss syndrome is a rare disorder that affects multiple organs especially the lungs. It is characterized by the abnormal clustering of certain white blood cells (hypereosinophilia) in the blood and tissues, inflammation of blood vessels (vasculitis), and the development of inflammatory nodular lesions called granulomas (granulomatosis). Most of the affected individuals have a previous history of allergy. Asthma and other lung abnormalities often precede the development of the generalized (systemic) symptoms and findings seen in Churg-Strauss syndrome by as little as six months or as much as two decades.
Churg-Strauss disease is said to account for slightly more than 2% of all vasculitic illnesses. The various primary systemic vasculitides (Churg-Strauss disease, PAN, microscopic polyangiitis, Wegener granulomatosis) together are estimated to affect 15-25 individuals per million individuals in North America annually. Little information is available concerning international variation in the prevalence or incidence of Churg-Strauss disease.