a group of genetically identical eosinophils derived from a significantly mutated ancestor cell. The clone may prove to be benign, pre-malignant, or overtly malignant. The fundamental driver of these hypereosinophilic (or uncommonly eosinophilic) disorders is the mutation which increases the proliferation, survival, and further mutation of cells descendant from the originally mutated cell. There are several subtypes of primary hypereosinophilia. Clonal hypereosinophilia
Clonal hypereosinophilia is hypereosinophilia caused by a pre-malignant or malignant clone of eosinophils that bear mutations in genes for PDGFRA, PDGFRB, or FGFR1 or, alternatively, a chromosome translocation that creates the PCM1-JAK2 fusion gene. These genes code for dysfunctional protein products capable of enhancing proliferation and/or survival of their parent cells which, in consequence, become an evolving and constantly growing clone of eosinophils. These mutations are recognized by the World Health Association as causing distinct entities differing from idiopathic hypereosinophilia and the idiopathic hypereosinophilic syndrome. Presence of these clones may be associated with tissue injury but in any case suggests specific therapy be directed at reducing the size and suppressing the growth of the eosinophil clone. More recently, mutations in other genes have been described as causing a similar type of clonal hypereosinophilia but have not yet been recognized as entities distinct from idiopathic hypereosinophilia and the idiopathic hyperesoniphilic syndrome. These include gene mutations in JAK2, ABL1, and FLT2 and chromosomal translocations that create the ETV6-ACSL6 fusion gene. Chronic eosinophilic leukemia (NOS)
Chronic eosinophilic leukemia, not otherwise specified (i.e.
Congenital disorders
Hyperimmunoglobulin E syndrome
Omenn syndrome
Familial eosinophilia

See also
Eosinophilia-myalgia syndrome

References
External links

Hypereosinophilic Syndrome research in UK
Hypereosinophilic Syndrome on patient.info
Hypereosinophilic Syndrome on eMedicine
Hypereosinophilic Syndrome (HES) on American Academy of Allergy, Asthma & Immunology
Hypereosinophilic syndrome on Mayo Clinic