Churg-Strauss syndrome (CSS) is an allergic, granulomatous angitis that is a variant of necrotizing vasculitis in which there is significant lung involvement. It also affects the musculoskeletal, cardiac, and peripheral nervous systems. CSS is sometimes referred to as polyarteritis nodosa with lung involvement.

The true incidence of CSS is uncertain, but it is less frequent than classic polyarteritis nodosa. It has been documented in all age groups but is extremely rare among infants.

The etiology of CSS is unknown; however, there is a strong association with allergic diathesis and frequently severe and/or intractable asthma.