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Hypereosinophilic Syndrome and Chronic Eosinophilic Leukaemia
The Hypereosinophilic Syndrome (HES) comprises a group of rare leukoproliferative disorders characterised by prolonged and sustained peripheral blood- and tissue eosinophilia leading to end-organ damage.1-3
HES is clinically heterogeneous, but has 3 hallmark features:3
- Sustained eosinophilia (total eosinophil count >1500/µL for >6 months)
- Absence of apparent etiologies for eosinophilia, including parasitic infections and allergic diseases
- Signs and symptoms of organ involvement
Like HES, patients with Chronic Eosinophilic Leukaemia (CEL) exhibit eosinophilia (≥1500/µL persisting >6 months) with evidence of organ involvement, having excluded the known causes of hypereosinophilia.4 [Kamineni et al, 2006; p1356a] However patients with CEL are distinguished from those with HES by the presence of an acquired cytogenetic mutation4 [Kamineni et al, 2006; p1356b] although no single or specific cytogenetic mutation or molecular genetic abnormality has been identified in CEL.5 [National Cancer Institute, 2009; p1a]
Epidemiology
The exact incidence of HES is unknown. According to 1 estimate, 1 or 2 new cases can be expected per year per 200,000 individuals.2 The disorder primarily affects males (male to female ratio, 9:1), and patients typically present between the ages of 20 and 50 years. There have been only a few reports of HES in children.3
The true incidence of CEL, like HES, is unknown because these disorders are so rare.4 [Kamineni et al, 2006; p1356c] However like HES, CEL has been reported to be more common in males, with peak incidence in the fourth decade of life.4 [Kamineni et al, 2006; p1356c]
References:
1. Chusid MJ, Dale DC, West BC, Wolff SM. The Hypereosinophilic Syndrome: analysis of fourteen cases with review of the literature. Medicine (Baltimore). 1975;54:1-27.
2. Karnak D, Kayacan O, Beder S, Delibalta M. Hypereosinophilic Syndrome with pulmonary and cardiac involvement in a patient with asthma. CMAJ. 2003;168:172-175.
3. Weller PF, Bubley GJ. The idiopathic Hypereosinophilic Syndrome. Blood. 1994;83:2759-2779.
4. Kamineni P, Baptiste A, Hassan M, et al. Case of Chronic Eosinophilic Leukemia with deletion of chromosome 16 and hepatitis C. J Natl Med Assoc 2006; 98(8):1356-1360.
5. National Cancer Institute. Chronic Eosinophilic Leukemia. Available online at: http://www.cancer.gov/cancertopics/pdq/treatment/myeloproliferative/HealthProfe ssional/page8. Accessed February 3, 2009.