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Genetic and Rare Diseases Information Center (GARD)

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Hypereosinophilic syndrome

Other Names for this Disease
  • HES
  • Hypereosinophilic syndrome, idiopathic
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Your Question

My younger brother was recently diagnosed with hypereosinophilic (HES) syndrome.  I would like to know if this condition has a genetic element.

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is hypereosinophilic syndrome?

Hypereosinophilic syndrome is a group of rare blood disorders characterized by increased levels of eosinophils (type of white blood cell that plays a role in the human immune system) persisting for more than six months with signs and symptoms due to involvement of the organs, most often the heart, the central and peripheral nervous system, lungs, and skin.[1][2][3]
Last updated: 6/22/2009

Is hypereosinophilic syndrome genetic?

In some cases, hypereosinophilic syndrome has been found to be genetic, with the person having a deletion in chromosome 4, specifically of 4q12. To learn more about chromosomes, click here. The deletion of 4q12 results in either the fusion of two genes, the FIP1-like-1 (FIP1L1) and platelet-derived growth factor receptor-alpha (PDGFRA) genes, or in the increased production of a interleukin (IL)-5 (a protein that plays a role in the human immune system) .  The fused FIP1L1-PDGFRA gene causes the changes cells in the bone marrow which lead to the increased levels of eosinophils. It has been found that some individuals with this specific chromosomal deletion respond well to treatment with imatinib.[3]
Last updated: 7/11/2011

Is hypereosinophilic syndrome hereditary?

As a quick review, the terms "genetic" and "hereditary" are often used interchangeably; however, they have different meanings. For example, a condition, like many cancers, may be genetic, but not hereditary, meaning that the genetic cause of the condition occur over time within that person and was not inherited from a parent. On the other hand, a condition that is genetic and is passed on within a family is hereditary.

In the case of hypereosinophilic syndrome, some cases have been discovered to be genetic, but not hereditary. There are also cases of hyperosinophilic syndrome that have been found to be both genetic and hereditary and are frequently referred to as familial eosinophilia.
Last updated: 6/22/2009

What is familial eosinophilia?

Familial eosinophilia (also called familial hypereosinophilia, familal hypereosinophilic syndrome, and hereditary eosinophilic syndrome) refers to a subgroup of hypereosinophilic syndrome that is characterized by persistent increased levels of eosinophilia and progression to end organ damage in some, but not all, affected family members. In general, familial eosinophilia has a more benign presentation than the other subgroups of hypereosinophilic syndromes.[4][5]
Last updated: 6/22/2009

Has the gene that causes familial eosinophilia been identified? How is the condition inherited?

Although the gene that causes familial eosinophilia has not been identified, it is believed that the gene that causes the disorder is located in the chromosomal area 5q31-q33 and that the condition is inherited in an autosomal dominant pattern.
Last updated: 7/11/2011

Who might I speak to if I am interested in determining whether familial eosinophilia is present in my family?

Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference at To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:  

Last updated: 7/11/2011

How can I find additional information and supportive resources for hypereosinophilic syndrome?

The GARD Web page on hypereosinophilic syndrome links to more online information and support resources. Click here to view the Web page.
Last updated: 6/22/2009

  • Hypereosinophilic syndrome. DermNet NZ. June 15, 2009; Accessed 6/22/2009.
  • Hypereosinophilic syndrome. Apfed Official Web site of the American Partnership for Eosinophilic Disorders. October 14, 2006; Accessed 6/22/2009.
  • Hypereosinophilic syndrome, idiopathic. OMIM (Online Mendelian Inheritance in Man). December 18, 2003; Accessed 6/22/2009.
  • Rioux JD, Stone VA, Daly MJ, Cargill M, Green T, Nguyen H et al. Familial Eosinophilia Maps to the Cytokine Gene Cluster on Human Chromosomal Region 5q31-q33. Am. J. Hum. Genet.. 1998;
  • Klion AD, Law MA, Riemenschneider W, McMaster ML, Brown MR, Horne M et al. Familial eosinophilia: a benign disorder?. Blood. 1 June 2004;