There is an ambiguous usage of the term "idiopathic hypereosinophilic syndrome". Previously it was used for all types of HES. Progress in research (see PMID:19630574 and Orphanet) has led to the concept of HES subtypes that can be distinguished on the basis of clinical and laboratory characteristics. According to these resources idiopathic hypereosinophilic syndrome as well as lymphoid hypereosinophilic syndrome (HES-L) and primary hypereosinophilic syndrome (HES-M) are subtypes of HES. However, this concept is not being used by all authors.
The diagnosis of hypereosinophilic syndrome is based on the following criteria (Chusid et al., 1975): sustained eosinophilia (more than 1,500 eosinophils per cubic millimeter) for more than 6 months; the absence of other causes of eosinophilia, including parasitic ... The diagnosis of hypereosinophilic syndrome is based on the following criteria (Chusid et al., 1975): sustained eosinophilia (more than 1,500 eosinophils per cubic millimeter) for more than 6 months; the absence of other causes of eosinophilia, including parasitic infections and allergies; and signs and symptoms of organ involvement, most frequently the heart, the central and peripheral nervous system, lungs, and skin. The clonality of hypereosinophilic syndrome has been demonstrated in some cases by clonal karyotypic abnormalities and X-inactivation assays (Luppi et al., 1994; Chang et al., 1999). Klion et al. (2003) concluded that elevated serum tryptase is a sensitive marker of a myeloproliferative variant of HES that is characterized by tissue fibrosis, poor prognosis, and imatinib responsiveness.
The hypereosinophilic syndrome is a rare hematologic disorder with sustained overproduction of eosinophils in the bone marrow, eosinophilia, tissue infiltration, and organ damage (Cools et al., 2003). The syndrome is more common in men than women (ratio of ... The hypereosinophilic syndrome is a rare hematologic disorder with sustained overproduction of eosinophils in the bone marrow, eosinophilia, tissue infiltration, and organ damage (Cools et al., 2003). The syndrome is more common in men than women (ratio of 9 to 1) and occurs predominantly between the ages of 20 and 50 years. Total leukocyte counts are usually less than 25,000 per cubic millimeter, with 30 to 70% eosinophils.
Cools et al. (2003) found that a hypereosinophilic syndrome patient being treated with imatinib had a complex chromosomal abnormality; this led to the identification of fusion of the FIP1L1 gene to the PDGFRA gene, which was caused by ... Cools et al. (2003) found that a hypereosinophilic syndrome patient being treated with imatinib had a complex chromosomal abnormality; this led to the identification of fusion of the FIP1L1 gene to the PDGFRA gene, which was caused by an interstitial deletion on chromosome 4q12. The resulting FIP1L1-PDGFRA gene was found to be a constitutively activated tyrosine kinase that transforms hematopoietic cells and is inhibited by imatinib. The authors subsequently detected the FIP1L1-PDGFRA gene in 9 of 16 patients with idiopathic hypereosinophilic syndrome and in 5 of the 9 patients with responses to imatinib that lasted more than 3 months. Relapse in 1 patient correlated with the appearance of a thr674-to-ile mutation in the PDGFRA gene (T674I; 173490.0008) that conferred resistance to imatinib. Griffin et al. (2003) found the 4q12 deletion in patients with HES, resulting in the same fusion gene involving PDGFRA and FIP1L1. They suggested that FIP1L1 be referred to as RAG (rearranged in hypereosinophilia). They demonstrated that the fusion kinase is constitutively phosphorylated and supports IL-3-independent growth when expressed in BaF3 cells. Proliferation and viability of EOL-1 and BaF3 cells expressing the fusion protein were ablated by imatinib and 2 other inhibitors of PDGFRA. The FIP1L1 and PDGFRA genes are both located in 4q12; the FIP1L1-PDGFRA fusion results from an apparent interstitial deletion that links FIP1L1 to exon 12 of PDGFRA.