Eosinophilia in children: characteristics, etiology and diagnostic algorithm.

Eosinophilia is common in children and may be caused by various disorders. Large-cohort studies, including mild cases, are limited in children. This study aimed to reveal underlying etiologies of childhood eosinophilia and to create a diagnostic algorithm. Children (< 18 years) with absolute eosinophil counts (AECs) ≥ 0.5 × 109/L were reviewed from medical files. Clinical characteristics and laboratory values were recorded. Patients were grouped based on the severity of eosinophilia as mild (0.5-1.5 × 109/L), moderate (≥ 1.5 × 109/L) and severe (≥ 5.0 × 109/L). An algorithm was formed to evaluate these patients. We included 1178 children with mild (80.8%), moderate (17.8%) and severe eosinophilia (1.4%). The most common reasons of eosinophilia were allergic diseases (80%), primary immunodeficiency (PID) (8.5%), infectious diseases (5.8%), malignancies (0.8%) and rheumatic diseases (0.7%). Only 0.3% of children presented with idiopatic hypereosinophilic syndrome. Allergic diseases and PIDs were the most common etiologies in mild/moderate and severe groups, respectively. The median duration of eosinophilia was 7.0 (3.0-17.0) months in the study population and was the shortest in severe cases (2.0 (2.0-5.0) months). Multiple logistic regression analysis demonstrated food allergy [OR:1.866, 95%CI:1.225-2.842, p = 0.004] and PIDs [OR:2.200, 95%CI:1.213-3.992, p = 0.009] as independent factors for childhood eosinophilia. A diagnostic algorithm including mild form was presented for childhood eosinophilia.    Conclusion: Eosinophilia was frequently determined due to secondary causes; allergic diseases in mild/moderate eosinophilia, PIDs in severe group. Etiology of eosinophilia was diverse, and an algorithm concerning the severity of eosinophilia would be practical and rational. What is Known: • In children, eosinophilia is common, and mild eosinophilia occurs frequently. • Malignancies presents frequently with severe eosinophilia. What is New: • Primary immunodeficiencies were not a rare cause of eosinophilia, especially in countries such as the Middle East and eastern Mediterranean countries, where the countries consanguineous marriages are common, and should be investigated in children with eosinophilia who do not have allergic or infectious diseases. • In literature, there are many algorithms about childhood hypereosinophilia. However, mild eosinophilia is extremely important in children. Because all patients with malignancy and most of the patients with rheumatic diseases presented with mild eosinophilia. Therefore, we proposed an algorithm for childhood eosinophilia that includes mild eosinophilia besides moderate and severe cases.

Diagnostic spectrum of hypereosinophilia based on bone marrow pathology: 10 years' experience at a tertiary care hospital.

BACKGROUND: Hypereosinophilia (HE) is defined as peripheral blood (PB) eosinophil count exceeding 1.5 × 109 /L. As the causes of HE can be diverse, the work-up of patients was complicated. In this study, we aimed to categorize the underlying diseases associated with HE and demonstrate minimum diagnostic approach. METHODS: Cases presenting with HE within 7 days of bone marrow (BM) examination conducted between 2008 and 2019 were selected. Cases were classified by the revised 2022 WHO and ICC classification. We also assessed morphologic features of unclassified persisting HE (>4 weeks) patients according to the morphologic criteria suggested a previous study by Wang et al. RESULTS: A total of 364 patients were included. The work-up confirmed primary HE in 38.7%, secondary HE in 48.9%, HE patients with insufficient evaluation in 13.7%. When conducted a slide review of HE patients with sustained HE more than 4 weeks among HE patients with insufficient evaluation, the morphological features showed abnormal eosinophils in PB/BM (69.0%/81.0%), hypercellularity (26.2%), myelofibrosis (7.1%), increased M:E ratio (5.3%), and dysmegakaryopoiesis (4.8%). Of these patients, 14 patients who met all morphologic criteria were suspected of CEL. CONCLUSIONS: This study demonstrates that HE is associated with variable conditions. BM morphological assessment based on a robust criterion can help to confirm a MN irrespective of the presence of clonal markers. The work-up of patients in whom ruled out the common secondary causes of HE requires a systematic but sufficient approach including at a minimum BM karyotyping, PDGFRA testing, lymphocyte immunophenotyping and TCR gene rearrangement.

Biologic therapies for hypereosinophilic disorders: From tyrosine kinase inhibitors to monoclonal antibodies. Towards an increasingly customized management?

Hypereosinophilic syndromes (HES) encompass a wide range of disorders characterized by persistent peripheral blood hypereosinophilia (HE) (i.e., an eosinophil count ≥1.5 × 109/L and ≥ 10% eosinophils preferably with a minimal duration of 6 months if documentation is available) associated with organ damage and/or dysfunction attributable to tissue eosinophilic infiltrate and release of granule contents. In most cases, HE is associated with atopic conditions/allergies, parasitic infections, medications, autoimmune disorders and/or solid tumors in most cases. More rarely, it can be one of the dominant manifestations of an underlying myeloid/lymphoid neoplasm. With regard to hematological forms, in recent decades the advances in understanding the pathogenic aspects of HES have led to a growing interest in these diseases, and in the 2016 WHO classification multiple subgroups were defined according to the molecular profile with the aim of better characterizing these syndromes and establishing which patients will benefit from specific pharmacological targeted therapies. This review article will provide a comprehensive overview of possible therapeutic approaches for HES in the light of each specific molecular alteration, considering both tyrosine kinase inhibitors and monoclonal antibodies, either implemented in clinical practice or currently still under development.

Proposed refined diagnostic criteria and classification of eosinophil disorders and related syndromes.

Eosinophilia and eosinophil activation are recurrent features in various reactive states and certain hematologic malignancies. In patients with hypereosinophilia (HE), HE-induced organ damage is often encountered and may lead to the diagnosis of a hypereosinophilic syndrome (HES). A number of known mechanisms and etiologies contribute to the development of HE and HES. Based on these etiologies and the origin of eosinophils, HE and HES are divided into primary forms where eosinophils are clonal cells, reactive forms where an underlying reactive or neoplastic condition is detected and eosinophils are considered to be "non-clonal" cells, and idiopathic HE and HES in which neither a clonal nor a reactive underlying pathology is detected. Since 2012, this classification and the related criteria have been widely accepted and regarded as standard. However, during the past few years, new developments in the field and an increasing number of markers and targets have created a need to update these criteria and the classification of HE and HES. To address this challenge, a Working Conference on eosinophil disorders was organized in 2021. In this conference, a panel of experts representing the relevant fields, including allergy, dermatology, hematology, immunology, laboratory medicine, and pathology, met and discussed new markers and concepts as well as refinements in definitions, criteria and classifications of HE and HES. The outcomes of this conference are presented in this article and should assist in the diagnosis and management of patients with HE and HES in daily practice and in the preparation and conduct of clinical trials.

Hematological hypereosinophilia / Hyperéosinophilies hématologiques

Introduction: Hematological disorders are the third cause of hypereosinophilia, after allergic and parasitic disease. The objective of our study is to show the epidemiological, clinical, biological and therapeutic characteristics of hematological hypereosinophilia. Patients and methods: This is a retrospective study over a 4-year period (March 2017-March 2021) concerning 14 patients with hematological hypereosinophilia. Results: Fourteen patients were included (9 women and 5 men). The median age at diagnosis was 55 years. Hematological hypereosinophilia was mainly of clonal etiology. Clinical manifestations were either specific to hypereosinophilia, such as organ damage, or related to the etiology of hypereosinophilia, such as hepato-splenomegaly and lymphadenopathy. Moderate and severe forms were the most commonly reported. Several other quantitative and qualitative abnormalities of the blood picture were reported. Identification of the FIP1L1-PDGFRA fusion gene by molecular biology (RT-PCR) was positive in two patients. Imatinib was the main treatment for clonal forms. Conclusion: Hematological hypereosinophilia is a rare and complex pathology. Our study has confirmed this epidemiological, clinical, biological and therapeutic heterogeneity and has enabled us to realize the contribution of molecular biology in the diagnosis and the treatment of hypereosinophilia.

Introduction: Les affections hématologiques représentent la troisième cause des hyper éosinophilies. L'objectif de notre travail est d'étudier les caractéristiques épidémiologiques, étiologiques, cliniques, biologiques et thérapeutiques des hyperéosinophilies hématologiques. Patients et méthodes: Il s'agit d'une étude rétrospective menée sur une période de 4 années (mars 2017-mars 2021). Cette étude a colligé 14 patients atteints d'hyperéosinophilie hématologique. Résultats: Quatorze patients ont été inclus (9 femmes et 5 hommes). L'âge médian au moment du diagnostic était de 55 ans. L'hyperéosinophilie hématologique était principalement d'étiologie clonale. Les manifestations cliniques étaient soit spécifiques à l'hyperéosinophilie telles que les atteintes d'organes, soit liées à l'étiologie de l'hyperéosinophilie telles que l'hépato-splénomégalie et les adénopathies. Les formes modérées et sévères étaient les plus fréquemment rapportées. Plusieurs autres anomalies quantitatives et qualitatives de l'hémogramme ont été rapportées. L'identification du gène de fusion FIP1L1-PDGFRA par biologie moléculaire (RT-PCR) était positive chez deux patients. L'imatinib était le traitement de choix des formes clonales. Conclusion: L'hyperéosinophilie hématologique est une pathologie rare et complexe. Notre étude a permis de confirmer cette hétérogénéité épidémiologique, étiologique, clinique, biologique et thérapeutique et de montrer l'apport de la biologie moléculaire dans le diagnostic et le traitement de cette pathologie.

Eosinophils and eosinophil-associated disorders: immunological, clinical, and molecular complexity.

Eosinophils and their mediators play a crucial role in various reactive states such as bacterial and viral infections, chronic inflammatory disorders, and certain hematologic malignancies. Depending on the underlying pathology, molecular defect(s), and the cytokine- and mediator-cascades involved, peripheral blood and tissue hypereosinophilia (HE) may develop and may lead to organ dysfunction or even organ damage which usually leads to the diagnosis of a HE syndrome (HES). In some of these patients, the etiology and impact of HE remain unclear. These patients are diagnosed with idiopathic HE. In other patients, HES is diagnosed but the etiology remains unknown - these patients are classified as idiopathic HES. For patients with HES, early therapeutic application of agents reducing eosinophil counts is usually effective in avoiding irreversible organ damage. Therefore, it is important to systematically explore various diagnostic markers and to correctly identify the disease elicitors and etiology. Depending on the presence and type of underlying disease, HES are classified into primary (clonal) HES, reactive HES, and idiopathic HES. In most of these patients, effective therapies can be administered. The current article provides an overview of the pathogenesis of eosinophil-associated disorders, with special emphasis on the molecular, immunological, and clinical complexity of HE and HES. In addition, diagnostic criteria and the classification of eosinophil disorders are reviewed in light of new developments in the field.

Idiopathic hypereosinophilic syndrome in hemodialysis patients: Case reports.

RATIONALE: Herein, we report 3 hemodialysis patients with idiopathic hypereosinophilic syndrome who were successfully treated using corticosteroid therapy. PATIENT CONCERNS: Case 1 was a 63-year-old man who was undergoing hemodialysis because of bilateral nephrectomy and developed hypereosinophilia with digestive symptoms, myocardial injury, and intradialytic hypotension. Case 2 was an 83-year-old man who was undergoing hemodialysis because of nephrosclerosis and developed hypereosinophilia with pruritus, myocardial injury, and intradialytic hypotension. Case 3 was a 59-year-old man who was undergoing hemodialysis because of diabetic nephropathy and developed hypereosinophilia with pruritus, myocardial injury, and intradialytic hypotension. DIAGNOSES: All 3 patients presented with hypereosinophilia (eosinophil count ≥1500 /µL for more than 1 month) and multiple-organ involvement (intradialytic hypotension, cardiac injury, digestive symptoms, and allergic dermatitis). A specific cause for the hypereosinophilia was not identified by systemic computed tomography, electrocardiography, echocardiography, bone marrow examination, or blood tests. Furthermore, Case 2 and 3 had not recently started taking any new drugs and drug-induced lymphocyte stimulation tests were negative in Case 1. Therefore, they were diagnosed with idiopathic hypereosinophilic syndrome. INTERVENTIONS: All 3 patients received corticosteroid therapy with prednisolone at a dose of 40 mg/d, 30 mg/d, and 60 mg/d in Case 1, 2, and 3, respectively. OUTCOMES: Their digestive symptoms, pruritus, intradialytic hypotension, and serum troponin I concentrations were immediately improved alongside reductions in their eosinophil counts. LESSONS: There have been few case reports of idiopathic hypereosinophilic syndrome in patients undergoing hemodialysis. We believe that recording of the clinical findings and treatments of such patients is mandatory to establish the optimal management of idiopathic hypereosinophilic syndrome.

Missed hypereosinophilic syndrome in a critically ill patient with systemic lupus erythematosus.

A high functioning 74-year-old man with systemic lupus erythematosus presented to the emergency department with acute anxiety. He was found to have elevated cardiac enzymes and admitted to the cardiology service for investigation. In hospital, he developed an erythematous papular rash, and deteriorated to being somnolent and bedridden. He was found to have new multiterritory ischaemic strokes. It was eventually noted that he had persistent eosinophilia, present even on admission, which had been overlooked as the total leucocyte count was normal. Serology for antiphospholipid antibody syndrome (APS) was positive. He was diagnosed with hypereosinophilic syndrome (HES) secondary to new APS, and responded to high-dose steroids. This case highlights the importance of fully evaluating a leucocyte differential to make a diagnosis of HES. We discuss the definition, clinical manifestations, diagnostic approach and management of this important condition.

B-acute Lymphoblastic Leukemia With Hypereosinophilia Associated With Severe Cardiac Complications: A Clinical Case.

Hypereosinophilia (HE) is rare but often secondary to a nonhematologic disease such as allergic disorders and parasitic infections. HE can also be associated with hematologic malignancies and be the result of a clonal proliferation or reactive to another hematologic condition. Association of HE with acute lymphoblastic leukemia (ALL) is rare in children. We reported a case of a teenager presented with HE secondary to B-ALL who experienced severe cardiac complications with severe absolute eosinophil count. We compared his clinical evolution with other published cases and we reported 2 mutations linked to B-ALL never described before in this context.

S100A8 and S100A9 Promote Apoptosis of Chronic Eosinophilic Leukemia Cells.

S100A8 and S100A9 function as essential factors in inflammation and also exert antitumor or tumorigenic activity depending on the type of cancer. Chronic eosinophilic leukemia (CEL) is a rare hematological malignancy having elevated levels of eosinophils and characterized by the presence of the FIP1L1-PDGFRA fusion gene. In this study, we examined the pro-apoptotic mechanisms of S100A8 and S100A9 in FIP1L1-PDGFRα+ eosinophilic cells and hypereosinophilic patient cells. S100A8 and S100A9 induce apoptosis of the FIP1L1-PDGFRα+ EoL-1 cells via TLR4. The surface TLR4 expression increased after exposure to S100A8 and S100A9 although total TLR4 expression decreased. S100A8 and S100A9 suppressed the FIP1L1-PDGFRα-mediated signaling pathway by downregulating FIP1L1-PDGFRα mRNA and protein expression and triggered cell apoptosis by regulating caspase 9/3 pathway and Bcl family proteins. S100A8 and S100A9 also induced apoptosis of imatinib-resistant EoL-1 cells (EoL-1-IR). S100A8 and S100A9 blocked tumor progression of xenografted EoL-1 and EoL-1-IR cells in NOD-SCID mice and evoked apoptosis of eosinophils derived from hypereosinophilic syndrome as well as chronic eosinophilic leukemia. These findings may contribute to a progressive understanding of S100A8 and S100A9 in the pathogenic and therapeutic mechanism of hematological malignancy.

Causes of hypereosinophilia in 100 consecutive patients.

BACKGROUND: Hypereosinophilia (HE, persistent peripheral blood eosinophilia > 1.5 × 109 /L) and hypereosinophilic syndrome (HES, HE with end-organ damage) are classified as primary (due to a myeloid clone), secondary (due to a wide variety of reactive causes), or idiopathic. Diagnostic evaluation of eosinophilia is challenging, in part because secondary causes of HE/HES such as lymphocyte-variant HES (L-HES) and vasculitis are difficult to diagnose, and emerging causes such as immunoglobulin G4-related disease (IgG4-RD) have rarely been examined. OBJECTIVE AND METHODS: We reviewed 100 consecutive patients with HE/HES who underwent extensive evaluation for primary and secondary eosinophilia at a single tertiary care center to determine causes of HE/HES in a modern context. RESULTS: Six patients had primary HE/HES, 80 had a discrete secondary cause identified, and 14 had idiopathic HE/HES. The most common causes of secondary eosinophilia were L-HES/HES of unknown significance (L-HESus) (20), IgG4-RD (9), and eosinophilic granulomatosis with polyangiitis (EGPA) (8). CONCLUSIONS: In contrast to other large published series of HE/HES, most patients in this study were found to have a discrete secondary cause of eosinophilia and only 14 were deemed idiopathic. These findings highlight the importance of extensive evaluation for secondary causes of eosinophilia such as L-HES, IgG4-RD, and EGPA.

Targeted Anti-IL-5 Therapies and Future Therapeutics for Hypereosinophilic Syndrome and Rare Eosinophilic Conditions.

Eosinophilic inflammation is a component of many atopic diseases such as asthma, and biologics targeting eosinophils have been shown to be effective in subsets of these patients. However, there also are conditions in which eosinophils are the key inflammatory cells responsible for driving tissue damage. In these eosinophilic diseases such as hyper-eosinophilic syndrome, eosinophilic esophagitis, and eosinophilic granulomatosis with polyangiitis (EGPA), the development of biologics inhibiting eosinophilic inflammation have offered targeted therapeutic strategies for patients that have not responded well to typical first line drugs, which often have significant adverse side effects with poor disease modification or recurrent relapse with significant morbidity. IL-5 has long been recognized as the key inflammatory cytokine involved in the priming and survival of eosinophils and their proliferation and maturation in eosinophilic disease. There are a number of trials and case series demonstrating the immunomodulatory benefits of anti-IL-5 therapies in these diseases with good clinical responses. Yet, due to the heterogeneity and rarity of these conditions, anti-IL-5 therapies have not resulted in disease remission for all patients. Clearly, further research into the use of anti-IL-5 therapies in various eosinophilic diseases is needed and ongoing investigation into other immune mechanisms underlying chronic eosinophilic diseases may provide alternative therapies for these challenging conditions.

Workup for eosinophilia.

With automated differentials being a common part of routine blood counts, the finding of eosinophilia is a relatively frequent occurrence. The first step in elucidating the cause is to determine the absolute eosinophil count (AEC), which is calculated from multiplying the percentage of eosinophils by the total white blood cell count. Eosinophilia is defined as an AEC of >500 eosinophils/µL, whereas hypereosinophilia is defined as an AEC of ≥1500 eosinophils/µL, a separation that is useful as an initial approach to the evaluation of such patients. Peripheral blood eosinophilia is most commonly secondary to allergies but can also be caused by certain infections, medication reactions, autoimmune diseases, or other conditions. However, hypereosinophilia is rarely, if ever, explained by allergy alone and should always prompt a further workup. A meticulous approach to exploring key aspects of the medical history is recommended for assessing increased AECs because it helps to narrow the list of possible etiologies, and treatment varies, depending on the underlying diagnosis. Special attention should be paid to the onset of eosinophilia and any coincident events, such as travel or the start of new medications. Another critical part of the history is a thorough attempt to identify any possible eosinophil-associated end-organ damage, although a biopsy of suspected involved areas is often necessary for confirmation. Because the causes of an elevated AEC are broad, determining the trigger or underlying disorder becomes an important intellectual riddle that can usually be solved with careful attention to history, physical examination, and appropriate laboratory work.