hematology and oncology
Hypereosinophilic Syndrome
Clonal hypereosinophilic syndromes
There are 2 broad subtypes of clonal hypereosinophilic syndrome (see table): Myeloproliferative variant Lymphoproliferative variant Themyeloproliferative variantis often associated with a small interstitial deletion in chromosome 4 at theCHIC2site that causes theFIP1L1/PDGFRA-associated fusion gene (which has tyrosine kinase activity that can transform hematopoietic cells). Patients often have Anemia Elevated serum tryptase levels Elevated serum vitamin B12 levels Hypogranular or vacuolated eosinophils Myelofibrosis Splenomegaly Thrombocytopenia Patients with the myeloproliferative subtype often develop endomyocardial fibrosis and may rarely develop Acute Myeloid Leukemia (AML) or ( General references ). Other cytogenetic abnormalities include rearrangement of the gene for fibroblast growth factor receptor 1 ( Some patients have chronic eosinophilic leukemia, in which blast cells are increased on bone marrow examination but not more than 20%. Thelymphoproliferative variantis associated with a clonal population of T cells with aberrant phenotype. Polymerase chain reaction (PCR) shows a clonal T-cell receptor rearrangement. Patients more often have Angioedema, skin abnormalities, or both Circulating immune complexes (sometimes with serum sickness) Hypergammaglobulinemia (especially high IgE) Patients with the lymphoproliferative variant also more often respond favorably to corticosteroids and occasionally develop T-cell lymphoma. include Gleich syndrome (episodic angioedema with eosinophilia), familial hypereosinophilic syndrome mapped to 5q 31-33, and other organ-specific syndromes. In organ-specific eosinophilic syndromes, eosinophilic infiltration is confined to a single organ (eg, eosinophilic gastrointestinal disease, Chronic Eosinophilic Pneumonia — Hyperleukocytosis may occur in patients with eosinophilic leukemia and very high eosinophil counts (eg,>100,000 cells/mcL [> 100 × 109/L]). Eosinophils can form aggregates that occlude small blood vessels, causing tissue ischemia and microinfarctions. Common manifestations include brain or lung hypoxia (eg, encephalopathy, dyspnea or respiratory failure). 