Löffler's syndrome or Loeffler's syndrome is a disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

 in which eosinophils accumulates in the lung

Lung

The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

 in response to a parasitic infection.

It was first described in 1932 by Wilhelm Löffler in cases of eosinophilic pneumonia

Eosinophilic pneumonia

Eosinophilic pneumonia is a disease in which a certain type of white blood cell called an eosinophil accumulates in the lung. These cells cause disruption of the normal air spaces where oxygen is extracted from the atmosphere. Several different kinds of eosinophilic pneumonia exist and can occur...

 caused by the parasites Ascaris lumbricoides

Ascaris lumbricoides

Ascaris lumbricoides is the giant roundworm of humans, belonging to the phylum Nematoda. An ascarid nematode, it is responsible for the disease ascariasis in humans, and it is the largest and most common parasitic worm in humans. One-sixth of the human population is estimated to be infected by this...

, Strongyloides stercoralis

Strongyloides stercoralis

Strongyloides stercoralis, also known as the threadworm, is the scientific name of a human parasitic roundworm causing the disease of strongyloidiasis....

and the hookworm

Hookworm

The hookworm is a parasitic nematode that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. A. duodenale predominates in the Middle East, North Africa, India...

s Ancylostoma duodenale

Ancylostoma duodenale

Ancylostoma duodenale is a species of the worm genus Ancylostoma. It is a parasitic nematode worm and commonly known as Old World hookworm. It lives in the small intestine of host such as humans, cats and dogs....

and Necator americanus

Necator americanus

Necator americanus is a species of Necator. It is a class within the phylum Nematodes and commonly known as New World hookworm. It is a parasitic nematode worm that lives in the small intestine of hosts such as humans, dogs and cats. It is responsible for Necatoriasis...

.

Although Löffler only described eosinophilic pneumonia in the context of infection, many authors give the term "Löffler's syndrome" to any form of acute onset pulmonary eosinophilia no matter what the underlying cause. If the cause is unknown, it is specified and called "simple pulmonary eosinophilia". Cardiac damage caused by the damaging effects of eosinophil granule proteins (ex. major basic protein

Major Basic Protein

Proteoglycan 2, bone marrow , also known as PRG2, is a protein which in humans is encoded by the PRG2 gene.- Function :...

) is known as Loeffler endocarditis

Loeffler endocarditis

Loeffler endocarditis, a form of endocarditis, is a form of hypereosinophilic syndrome.It is a restricive cardiomyopathy characterized eosinophilia and eosinophilic penetration leading to the fibrotic thickening of portions of the heart and commonly has large mural thrombi. Common symptoms include...

and can be caused by idiopathic eosinophilia or eosinophilia in response to parasitic infection.

The disease is in the differential diagnosis of wheezing.