Eosinophilic disorders: molecular pathogenesis, new classification, and modern therapy

Area of Science:

• Hematology
• Molecular Biology
• Oncology

Background:

• Historically, hypereosinophilia without clear cause was termed idiopathic hypereosinophilic syndrome (HES).
• Lack of identifiable reactive causes led to this 'idiopathic' classification.
• Limited understanding of underlying pathophysiology hindered specific diagnoses.

Purpose of the Study:

• To review recent advances in understanding the molecular basis of eosinophilic disorders.
• To highlight the shift from idiopathic diagnoses to genetically defined conditions.
• To discuss the implications for classification and targeted therapy.

Main Methods:

• Review of recent molecular and genetic discoveries in eosinophilic disorders.
• Analysis of diagnostic shifts from idiopathic HES to specific genetic entities.
• Examination of therapeutic strategies targeting identified molecular abnormalities.

Main Results:

• Identification of recurrent molecular abnormalities, particularly fusion tyrosine kinases, in eosinophilic disorders.
• Discovery of the FIP1L1-PDGFRA fusion gene in a subset of HES and systemic mast cell disease.
• Recognition of PDGFRA, PDGFRB, and FGFR1 rearrangements in eosinophilic chronic myeloproliferative disorders.
• Identification of aberrant T-lymphocytes secreting cytokines like IL-5 in lymphocyte-mediated hypereosinophilia.

Conclusions:

• Molecular advances have redefined idiopathic HES as genetically specific clonal eosinophilias.
• Targeted therapies, such as imatinib mesylate and anti-IL-5 antibodies, are effective for these genetically defined diseases.
• Improved understanding of eosinophilic disorder pathophysiology enables more precise classification and treatment.