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Hypereosinophilic Syndromes. Eosinophils – The Basics. Produced in the bone marrow Function to combat parasitic infections, ectoparasites, certain viral infections, and amplify responses of mast cells in atopy
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Eosinophils – The Basics • Produced in the bone marrow • Function to combat parasitic infections, ectoparasites, certain viral infections, and amplify responses of mast cells in atopy • This is largely accomplished by generating ribonucleases, oxidative species = apoptosis, and inducing degranulation of basophils and mast cells • Eosinophils are attracted to tissues by certain chemokines (RANTES, CCL11/24) and leukotrienes • They require IL-5 (Eosinophil growth factor, secreted by T-cells) for proliferation and to prevent apoptosis • They are VERY sensitive to steroids
Eosinophils – The Basics • These granules are full of: • Major Basic Protein = toxic to helminths and epithelial cells • Ribonuclease A (aka Eosinophil Cationic Protein) • Eosinophil Peroxidase = generation of hypobromite used to combat Helminths and TB • Proteases that are involved in tissue remodeling
Hypereosinophilic Syndromes • Represents a heterogenous group of uncommon disorders marked by blood or tissue eosinophilia • Known causes of secondary or reactive eosinophilia must be ruled out • Range from benign idiopathic eosinophilia to eosinophilic leukemia • Pretty rare, 50 total documented cases between 1971 – 1982 • Previously defined by Chusid et al in 1975 by the following: • Greater than or equal to 1500 eosinophils/mm3 for at least 6 months • Lack of evidence for secondary etiologies of hypereosinophilia • Presumptive signs and symptoms of organ involvement
Hypereosinophilic Syndromes • Secondary (reactive) causes of eosinophilia
Hypereosinophilic Syndromes • Main DDx include: • Systemic mastocytosis • Occult malignancy, solid (adenocarcinoma) or liquid (leukemia/lymphoma) • Churg Strauss • Atopy • Parasitic infections • Chronic TB • Other granulomatous disease such as sarcoid and IBD • Endocrine causes such as hypoadrenalism • Morbidity and mortality associated with these syndromes = usually due to cardiac and neuropathic complications • These represent medical emergencies that require emergent treatment with corticosteroids
Hypereosinophilic Syndromes • Primary cardiac complications include cardiogenic shock or heart failure due to • Loeffler’s endocarditis = a restrictive cardiomyopathy from eosinophilic infiltration leading to fibrotic thickening • Endomyocardial fibrosis (aka Davies Disease, seen in the tropics) • Other clinical manifestations include: • Skin and mucosal ulcerations • Thromboembolic disease • Splenomegaly • Pleural effusions and/or pulmonary fibrosis
Hypereosinophilic Syndromes • More recent analyses differentiate the spectra of hypereosinophilic diseases as the following varients: • FIP1L1/PDG positive, aka myeloproliferative variant HES • Lymphocyte variant HES = significant eosinophilopoiesis • Familial HES • Associated HES (from reactive eosinophilia) • Overlap HES
Clinical Approach • CBC with diff, serum tryptase, strongyloides antibody, peripheral lymphocyte clonal studies • Bone marrow biopsy with FISH/Flow, ANA, SPEP • TTE, CT chest and abdomen
Treatment • Corticosteroids 1mg/kg/day with good success • Imatinib therapy if the FIP1L1/PDG fusion protein is present • Anti-IL-5 therapy with mepolizumab
References • Klion, A. How I treat hypereosinophilic syndromes. Blood, 2009;114(18):3736-3741 • Chusid, DC et al. The hypereosinophilic syndrome. Medicine. 1975;54(1):1-27 • Cools, J et al. A tyrosine kinase created by fusion of the PDGFRA and FIP1L1 genes as a therapeutic target of imatinib in idiopathic hypereosinophilic syndrome. New England Journal of Medicine. 2003;348(13):1201-1214