of deterioration regularly. Many cases of hypereosinophilic syndrome may be treated exclusively with monoclonal antibodies such as mepolizumab It may then be typical not to prescribe corticosteroids for this condition, reducing the burden of the side effects associated with corticosteroids. Epidemiology The European Medicines Agency (EMA) estimated the prevalence of HES at the time of granting orphan drug designation for HES in 2004 at 1.5 in 100,000 people, corresponding to a current case load of about 8,000 in the EU, 5,000 in the U.S., and 2,000 in Japan. Patients without chronic heart failure and those who respond well to pharmaceutical treatments have a good prognosis. However, the mortality rate rises in patients with anaemia, chromosome abnormalities or a very high white blood cell count. History Hypereosinophilic syndrome was first described as a distinct entity by Hardy and Anderson in 1968. References External links Hypereosinophilic Syndrome on patient.info on eMedicine Eosinophilic cutaneous conditions Myeloid neoplasia Monocyte and granulocyte disorders