Hypereosinophilic syndromes (HES) are types of disorders that happen when eosinophils (white blood cells) are overproduced by a person’s body.
These white blood cells then attack organ systems like the skin, lungs, brain/nerves and heart. This can result in illness due to these organs not working properly. Some specific genetic abnormalities have been discovered as the underlying cause of some hypereosinophilic syndromes, but in many cases a specific cause cannot be identified. In these cases, the diagnosis is called idiopathic (unknown) hypereosinophilic syndrome.