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HES is a syndrome (i.e., a collection of similar entities), not a disease, characterized by the simultaneous existence of (1) eosinophil count greater than 1500/mm3 for more than 6 months, (2) absence of any known cause of eosinophilia, and (3) existence of symptoms of organ involvement (benign eosinophilia is excluded).

Idiopathic Hypereosinophilic Syndrome.

Leukoproliferative disorder of unknown origin characterized by overproduction of eosinophils that results in multiple organ damage. First described by Hardy and Anderson in 1968.

Not known but rare. No racial predilection is reported, but male-to-female ratio is 9:1 (male predominance). Survival rate is 80% at 5 years and 42% at 10 years.


The etiology of this syndrome is unknown, but it is characterized by proliferation of eosinophils. These cells damage tissue, especially cardiac and neural tissue, by release of peroxidase and neurotoxin. The production of eosinophil is regulated by several cytokines (IL-3, GM-CSF, IL-5). Usually, eosinophils reach areas of inflammation and quickly undergo apoptosis after degranulation. In HES, eosinophils survive longer in the tissues, thus increasing the amount of damage they can inflict because they store (and release) toxic cationic proteins, which are the primary mediators of tissue damage. The most serious complication of HES is cardiac involvement (myocardial fibrosis and congestive heart failure); however, hypereosinophilia alone is insufficient to cause cardiac damage.

Leukocytosis with eosinophilia. Bone marrow examination is required to rule out eosinophilic leukemia. Treatable parasitic infections must be sought. Some cases previously diagnosed as HES involved malignant transformation of eosinophils, but these constitute a minority and malignant evolution and are not a feature of HES.

HES is a heterogenous disease process. Multiple clinical manifestations may occur simultaneously or individually. Central nervous system (CNS) dysfunction (confusion, delirium, coma, dementia), congestive heart failure, arrhythmias, pulmonary infiltrates/effusion, nonproductive cough, hepatosplenomegaly, anemia and/or thrombocytopenia, anorexia, weight loss, fatigue, nausea, abdominal pain, diarrhea, pruritic rash, fever, night sweats, hepatosplenomegaly, peripheral neuritis, and venous thrombosis. Most commonly diagnosed between 20 and 50 years of age; rare in children.

Baseline neurologic examination must be obtained. Evaluate for cardiac dysfunction and arrhythmia. Review baseline chest radiographs, ECG, cell blood count (CBC), and liver function. Echocardiography is recommended.

Avoid regional anesthesia if thrombocytopenia is present.

Avoid myocardial depressants. Prophylaxis against thrombosis postoperatively.

Other syndromes with eosinophilia, especially the following:

Churg-Strauss Syndrome (Allergic Granulomatous Angiitis): Autoimmune disorder affecting smallto medium-sized arteries and veins, associated with antibodies to neutrophil cytoplasmic antigens; symptoms include asthma, asthenia, weight loss, fever, purpura, eosinophilia, anemia, and multivisceral disorders.

Eosinophilia-Myalgia Syndrome: Multisystemic, chronic, autoimmune disease caused by ingestion of impure l-tryptophan (usually ingested as an amino acid dietary supplement).

Kimura Disease: Chronic inflammatory disorder of unknown origin, characterized by solitary or multiple nonpainful subcutaneous nodules located on the head or neck with peripheral ...

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