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What is Hypereosinophilic syndrome and explain in detail?
Hypereosinophilic syndrome  is a disease characterized by a persistently elevated eosinophil count (≥ 1500 eosinophils/mm³) in the blood for at least six months without any recognizable cause, with involvement of either the heart, nervous system, or bone marrow.HES is a diagnosis of exclusion, after clonal eosinophilia (such as FIP1L1-PDGFRA-fusion induced hypereosinophelia and leukemia) and reactive eosinophilia (in response to infection, autoimmune disease, atopy, hypoadrenalism, tropical eosinophilia, or cancer) have been ruled out.There are some associations with chronic eosinophilic leukemia as it shows similar characteristics and genetic defects.
If left untreated, HES is progressive and fatal. It is treated with glucocorticoids such as prednisone. The addition of the monoclonal antibody mepolizumab may reduce the dose of glucocorticoids.

Signs and symptoms
As HES affects many organs at the same time, symptoms may be numerous. Some possible symptoms a patient may present with include:

Cardiomyopathy
Skin lesions
Thromboembolic disease
Pulmonary disease
Neuropathy
Hepatosplenomegaly
Reduced ventricular size
Atopic eczema

Diagnosis
Numerous techniques are used to diagnose hypereosinophilic syndrome, of which the most important is blood testing. In HES, the eosinophil count is greater than 1.5 × 109/L. On some smears the eosinophils may appear normal in appearance, but morphologic abnormalities, such as a lowering of granule numbers and size, can be observed