Churg-Strauss syndrome is a disorder marked by blood vessel inflammation. This inflammation can restrict blood flow to vital organs and tissues, sometimes permanently damaging them. This condition is also known as eosinophilic granulomatosis (gran-u-low-muh-TOE-sis) with polyangiitis (pol-e-an-jee-I-tis).Churg-Strauss syndrome is a highly variable illness. Some people have only mild symptoms. Others experience severe or life-threatening complications. Churg-Strauss syndrome has three stages, or phases, each with its own signs and symptoms. Not everyone develops all three phases. Nor do the phases always arise in the same order. This is especially true when the disease is caught and treated before the most serious damage occurs. Allergic stage, eosinophilic stage and vasculitic stage.The exact cause of Churg-Strauss syndrome is unknown. It's likely that an overactive immune system response is triggered by a combination of genes and environmental factors, such as allergens or certain medications. Instead of simply protecting against invading organisms such as bacteria and viruses, the immune system overreacts and targets healthy tissue, causing widespread inflammation.