Loeffler endocarditis is a rare condition that affects the heart, causing inflammation and scarring of the heart tissues. This condition is also known as eosinophilic myocarditis or idiopathic hypereosinophilic syndrome. Eosinophilic myocarditis is a type of myocarditis, which is an inflammation of the myocardium, the heart muscle. The Loeffler endocarditis name originated from the German physician Wilhelm Loeffler, who first described the condition in 1936. Other synonyms for Loeffler endocarditis include Loeffler syndrome, Loeffler endomyocarditis, Loeffler's disease, and idiopathic eosinophilic endomyocarditis. This condition can be life-threatening and requires immediate medical attention.