The hypereosinophilic syndromes: current concepts and treatments

Hypereosinophilic syndrome in Europe: Retrospective study of treatment patterns, clinical manifestations, and healthcare resource utilization

BACKGROUND

The burden of hypereosinophilic syndrome (HES) in Europe is not well characterized.

OBJECTIVE

To evaluate real-world patient characteristics, treatment patterns, clinical manifestations, and healthcare resource utilization for patients with HES from France, Germany, Italy, Spain, and the United Kingdom.

METHODS

In this retrospective, noninterventional study, data for patients with a physician-confirmed diagnosis of HES were abstracted from medical chart reviews. Patients were aged 6 years or older at the time of HES diagnosis and had 1 or more years of follow-up from the index date (first clinic visit between January 2015 and December 2019). Data on treatment patterns, comorbidities, clinical manifestations, clinical outcomes, and healthcare resource utilization were collected from diagnosis or index date to end of follow-up.

RESULTS

Data for 280 patients were abstracted from medical charts by 121 physicians treating HES, with multiple specialties. Most patients (55%) had idiopathic HES, and 24% had myeloid HES; the median number (interquartile range [IQR]) of diagnostic tests per patient was 10 (6-12). The most common comorbidities were asthma (45%) and anxiety or depression (36%). Most patients (89%) used oral corticosteroids; 64% used immunosuppressants or cytotoxic agents, and 44% used biologics. Patients had a median (IQR) of 3 clinical manifestations (1-5), most commonly constitutional (63%), lung (49%), and skin (48%). Twenty-three percent of patients experienced a flare, and 40% had a complete treatment response. Some patients (30%) were hospitalized with a median (IQR) stay of 9 days (5-15) for HES-related issues.

CONCLUSION

Patients with HES across 5 European countries had a substantial disease burden despite extensive oral corticosteroids treatment, highlighting the need for additional targeted therapies.

Resolved Hypereosinophilic Syndrome and Immune Thrombocytopenic Purpura in Ulcerative Colitis Patients Post Colectomy: A Case Series and Literature Review

Introduction

Hypereosinophilic syndrome (HES) and immune thrombocytopenic purpura (ITP) have been reported to co-occur with ulcerative colitis (UC). However, the exact pathogenic mechanisms of their occurrence remain elusive. In this article, we aim to describe two cases of UC patients who developed refractory HES and ITP and elaborate on their potential pathogenesis.

Case Study

We report two middle-aged patients diagnosed with UC. The first patient developed HES that was refractory to conventional medical therapy of idiopathic HES, and the second developed refractory ITP that failed steroid and immunosuppressive therapy. Both conditions improved considerably following colectomy, suggesting they are of a reactive rather than idiopathic nature.

Conclusion

In patients with UC and refractory comorbid HES or ITP, the reactive nature of these comorbidities should be taken into consideration, and colectomy, therefore, should be considered if clinically indicated.

Episodic Angioedema with Hypereosinophilia (Gleich's Syndrome): A Case Report and Extensive Review of the Literature

Episodic angioedema with eosinophilia (EAE) (Gleich's syndrome) is a rare disease characterized by hypereosinophilia (up to 95 × 10⁹ cells/L), recurrent episodes of angioedema, urticaria, weight gain, and fever, that occur at periodical intervals (usually every 3-4 weeks). The exact etiology of EAE is still unclear, but both eosinophils and abnormalities of cytokines homeostasis seem to play a pivotal role in the pathogenesis of the disease. In particular, the cyclic elevation of serum interleukin-5 before the increase in eosinophil count has been reported. Herein, we performed a broad literature review and report the case of a thirty-two-year-old woman with a two-year history of cyclic angioedema attacks, urticaria, periodic weight gain, and severe hypereosinophilia, diagnosed with EAE and treated with oral corticosteroids. Describing the most relevant clinical features of EAE reported so far in the literature, we aim to provide physicians with some useful tools to help them deal with this disease. In addition, we aim to raise awareness about this rare condition in which approved diagnostic classification criteria are currently missing.

Targeting eosinophils in respiratory diseases: Biological axis, emerging therapeutics and treatment modalities

Eosinophils are bi-lobed, multi-functional innate immune cells with diverse cell surface receptors that regulate local immune and inflammatory responses. Several inflammatory and infectious diseases are triggered with their build up in the blood and tissues. The mobilization of eosinophils into the lungs is regulated by a cascade of processes guided by Th2 cytokine generating T-cells. Recruitment of eosinophils essentially leads to a characteristic immune response followed by airway hyperresponsiveness and remodeling, which are hallmarks of chronic respiratory diseases. By analysing the dynamic interactions of eosinophils with their extracellular environment, which also involve signaling molecules and tissues, various therapies have been invented and developed to target respiratory diseases. Having entered clinical testing, several eosinophil targeting therapeutic agents have shown much promise and have further bridged the gap between theory and practice. Moreover, researchers now have a clearer understanding of the roles and mechanisms of eosinophils. These factors have successfully assisted molecular biologists to block specific pathways in the growth, migration and activation of eosinophils. The primary purpose of this review is to provide an overview of the eosinophil biology with a special emphasis on potential pharmacotherapeutic targets. The review also summarizes promising eosinophil-targeting agents, along with their mechanisms and rationale for use, including those in developmental pipeline, in clinical trials, or approved for other respiratory disorders.

Idiopathic hypereosinophilic syndrome with intracardiac atypical linear-shaped and floating thrombus presenting as embolic cerebral infarction

Knowledge of the multi-organ involvement in hypereosinophilic syndrome (HES) is important for the diagnosis and care of patients with this condition, even in cases with atypical presentation. This report aims to describe cerebral embolic infarction and intracardiac atypical linear-shaped thrombus in a patient with idiopathic HES and to discuss the approach of appropriate diagnosis and timely interventional management. A 55-year-old man presented with general weakness, including left-sided weakness, mild cognitive dysfunction, and mild exertional dyspnea for about 2 weeks. Initial magnetic resonance imaging for evaluating the brain showed multifocal acute to subacute infarction of both cerebral hemispheres and both cerebellums. Laboratory findings revealed leukocytosis (25,620 cells/mm³) and eosinophilia (54.9%). To evaluate the intracardiac embolic source, the patient underwent echocardiography, and a 1.5 cm linear thread-like and mobile mass was detected. Consequently, the patient was diagnosed with idiopathic HES. After bone marrow biopsy, corticosteroid and hydroxyurea were administered to control the eosinophilia. This case indicates that HES can present as a floating intracardiac atypical linear-shaped thrombus attached to the left ventricle. After appropriate diagnostic approaches, proper treatment could be given for the patient. <Learning objective: Idiopathic hypereosinophilic syndrome (HES) is a disorder characterized by persistent eosinophilia with heterogeneous clinical manifestations. Knowledge of the multi-organ involvement in HES is important for the diagnosis and care of patients with this condition, even in cases with atypical shaped thrombus as clinical presentation. Close monitoring combined with early treatment and diagnosis may help reduce mortality in HES patients.>.

Hypereosinophilic Syndrome, Multiorgan Involvement and Response to Imatinib

Hypereosinophilic syndrome (HES) is an uncommon syndrome characterized by peripheral blood eosinophils count of more than 1,500/mm³ with associated tissue damage. It can be either primary or secondary, for example, due to parasitic infections or inflammation.

We present a case of a 49-year-old Asian female with recurrent hospital admissions for cholecystitis, gastritis, urinary cystitis, and pancreatitis. Her peripheral blood count showed excessive eosinophils 15,600-19,000/mm³ on different occasions. Pathology of her gallbladder and her gastric biopsies showed eosinophilic infiltration. Her bone marrow biopsy showed a normocellular marrow with active trilineage hematopoiesis, eosinophilia, mild megakaryocytic hyperplasia with a few atypical forms, and mild T-cell lymphocytosis. Flow cytometry showed no evidence of acute leukemia, or T-cell or B-cell lymphoproliferative disorder. On fluorescent in-situ hybridization (FISH), myeloproliferative neoplasms (MPN) testing was negative for platelet-derived growth factor receptor-alpha (PDGFRA), platelet-derived growth factor receptor-beta (PDGFRB), and fibroblast growth factor receptor-1 (FGFR1) rearrangement. Despite not having the FIP1L1‐PDGFRA (factor interacting with PAPOLA and CPSF1-platelet-derived growth factor receptor, alpha polypeptide) gene fusion, our patient responded to the treatment with a significant decrease in her absolute eosinophils count and resolution of her symptoms.

Budd-Chiari Syndrome Associated With Hypereosinophilic Syndrome Treated by Deceased-Donor Liver Transplantation: A Case Report

INTRODUCTION

Budd-Chiari syndrome (BCS) associated with hypereosinophilic syndrome (HES) is very rare, and only a few reports have described its treatment. Furthermore, no report to date has described the performance of liver transplantation for the treatment of BCS associated with HES. We herein describe a 54-year-old man who underwent deceased-donor liver transplantation (DDLT) for treatment of BCS associated with HES.

CASE

A 54-year-old man was found to have an increased eosinophil count during a medical check-up. After exclusion of hematopoietic neoplastic diseases and secondary eosinophilia, idiopathic hypereosinophilia was diagnosed. Oral prednisolone was administered to the patient, and his eosinophil count immediately decreased to a normal level. He had an uneventful course without complications for 11 months but then presented with bloating and malaise. Imaging studies including ultrasonography, enhanced computed tomography, and angiography revealed BCS associated with HES. Transjugular intrahepatic portosystemic shunt failed because of complete obstruction of the hepatic veins. Therefore, the patient was introduced to our hospital for liver transplantation. DDLT was performed with venovenous bypass 1 month after the patient was placed on the DDLT waiting list. The explanted hepatic veins were completely occluded and organized. The patient's eosinophil count was maintained at a normal level with prednisolone treatment after DDLT.

CONCLUSIONS

Liver transplantation can be a treatment option for BCS associated with HES if neoplastic diseases and secondary eosinophilia have been excluded. Life-long oral steroid therapy is required to control HES even after liver transplantation.

Hypereosinophilic dermatitis: generalised lichenification and gyrate erythema as the sole manifestation of idiopathic hypereosinophilic syndrome

A 22-year-old female presented with generalised lichenification and severe pruritus, along with multiple annular papules and concentric plaques over trunk and extremities for the last 3 years. Her haematological investigations revealed leucocytosis with peripheral blood eosinophilia and raised serum IgE levels. Skin biopsy showed perivascular and interstitial infiltrate of eosinophils and lymphocytes in the dermis. Bone marrow examination showed myeloid hypercellularity with increased number of eosinophils, but no atypical cells. Cytogenetic studies did not reveal any chromosomal alterations. No systemic involvement was found on imaging. A diagnosis of idiopathic skin-limited hypereosinophilic syndrome was made. She was treated with tapering doses of oral prednisolone and weekly methotrexate with significant improvement in skin lesions and pruritus in 2 months, which was maintained at 7-month follow-up.

A complex and cryptic intrachromosomal rearrangement generating the FIP1L1_PDGFRA in adult acute myeloid leukemia

Myeloid neoplasms with eosinophilia and abnormalities of the PDGFRA gene can benefit from therapy with tyrosine kinase inhibitors, therefore revealing the PDGFRA rearrangement is essential to ensure the best choice of treatment. The most common PDGFRA partner is the FIP1L1 gene, generating the oncoprotein FIP1L1/PDGFRA (F/P). In the majority of cases the F/P fusion gene originates from intrachromosomal rearrangement at band 4q12, and occasionally from chromosomal translocations. In both cases, the interstitial chromosomal deletion of a region involving the CHIC2 gene has been reported, which is cryptic by conventional karyotyping but detectable by Fluorescence In Situ Hybridization (FISH) analyses. Herein, we report an acute myeloid leukemia (AML) case presenting with eosinophilia; the F/P fusion gene originated from a new, cryptic and complex intrachromosomal rearrangement of 4q12. Classical FISH assay revealed abnormal hybridization signals, but the presence of the F/P chimaeric gene was demonstrated by molecular analysis. We performed molecular characterization of the chromosomal rearrangement and targeted Next-Generation Sequencing (NGS) analysis with a myeloid gene panel, revealing the presence of pathogenic genomic variants affecting the TET2 and ETV6 genes. These mutations were present as subclones at the disease onset and their clone size increased at relapse.

Clonal evolution revealed by next-generation sequencing in a long-term follow-up patient with hypereosinophilia

The natural history of primary hypereosinophilia remains poorly defined, given the underlying disease heterogeneity. Recently, targeted NGS helps to establish clonality in a subset of patients with hypereosinophilia. We first reported the clonal evolution in a long-term follow-up patient with hypereosinophilia. This case initially presented with chronic eosinophilic leukemia, not otherwise specified (CEL-NOS), successively transformed to myelodysplastic syndromes (MDS) and acute myeloid leukemia(s-AML). We identified three mutations at CEL-NOS phase, five and seven mutations at MDS and s-AML stages, respectively. Our data illustrate the clonal dynamic process associated with disease evolution from CEL-NOS to s-AML.

Hypereosinophilic vasculitis: A case report

INTRODUCTION

The Revised International Chapel Hill Consensus Conference 2012 subdivides vasculitides based on combinations of features that separate different forms of vasculitis into definable categories. Hypereosinophilic vasculitis with sparing of the respiratory tract and renal system is a rare presentation that is yet to be described in the Revised International Chapel Hill Consensus Conference 2012 report that addresses nomenclature of vasculitides. This is a condition that involves a vascular injury due to either a primary eosinophilic vasculitis or an underlying connective tissue disease and it predisposes patients to a prothrombotic state.

PATIENT CONCERNS

A 39-year-old patient presented with left hand digital ischemia, preceded by Raynaud phenomenon, and vasculitic rash. For 3 months, he was having digital ischemia affecting the left 2nd and 3rd digits in the form of pallor and gangrenous discoloration with a preceding history of a pinpoint pruritic rash affecting his lower limbs that extended to involve the trunk and upper limbs over a short period of time and responded to only a tapering dose of oral steroids. Examination revealed a delayed capillary refill in all left-hand digits and a weak left radial pulse but no bruit. The rest of his peripheral vascular examination was unremarkable.

DIAGNOSIS

Investigations revealed an absolute eosinophilic count of 4.34 K/μL and erythrocyte sedimentation rate of 44 mm/h. A magnetic resonance angiogram showed a beaded appearance of the left ulnar artery distally and the radial artery branches in the left hand and subsequently was diagnosed with hypereosinophilic vasculitis.

INTERVENTIONS

He was started on oral prednisone of 1 mg/kg daily orally tapering done as well as azathioprine for maintenance.

OUTCOMES

Two weeks postdischarge, the patient was seen in the outpatient department where his ischemic symptoms improved, and his skin rash healed. Noticed improvement in his splinter hemorrhages was also detected. He continued to do well on 2 years follow-up CONCLUSION:: This case reflects the importance of frequent reevaluation for vasculitic diseases criteria and nomenclature. Hypereosinophilic vasculitis with absent respiratory and renal involvement is a rare presentation with scarce evidence to guide treatment.

Mepolizumab-a novel option for the treatment of hypereosinophilic syndrome in childhood

BACKGROUND

Mepolizumab was originally intended as a therapeutic agent for atopic asthma in adults, and consequently, little is known about its use in children. Up to now, corticosteroids have formed the basis of the initial treatment of hypereosinophilic syndromes and are shown to be effective in most patients. To analyze the effect of mepolizumab in children is the aim of this study.

METHODS

We are reporting the experience of the effect of mepolizumab in 2 pediatric patients with hypereosinophilic syndrome that was not sufficiently controlled by other drugs. In addition, the literature regarding the treatment with mepolizumab in pediatric and adult patients is reviewed for the most important studies regarding safety and efficacy.

RESULTS

Mepolizumab therapy showed in 2 pediatric patients with severe hypereosinophilic syndrome a safe and efficient therapeutic approach. No significant intolerances appeared. Furthermore, treatment with systemic corticosteroids was terminated, and therefore, severe side effects were avoided in our pediatric cases.

CONCLUSIONS

Anti-IL-5 antibodies, which can be applied without substantial drug intolerances, are a new, safe, and effective treatment option for pediatric patients with hypereosinophilic syndrome.

Hypereosinophilic syndrome with central nervous system involvement: Two case reports and literature review

OBJECTIVE

To report two cases of hypereosinophilic syndrome (HES) with central nervous system involvement and explore its possible pathogenesis.

METHODS

We have analysed the clinical data and relevant features of two patients who presented themselves to The Affiliated Hospital of Xuzhou Medical University between 2012 and 2015. We have reviewed the relevant literature, elaborated the possible pathogenesis, and discussed the treatment options.

RESULTS

Both patients had consistently high levels of absolute eosinophil count which led to multiple cerebral infarcts in the arterial border zone and small-vessel disease. Blood tests were taken several times during their course of disease showing elevated eosinophils. Both patients underwent head computed tomography (CT), magnetic resonance imaging, and magnetic resonance angiography, which indicated small-vessel disease and watershed infarction. Glucocorticoids, improvement cycle, and neuro-nutrition treatments resulted in a significant improvement of their clinical state.

CONCLUSION

HES can involve central nervous system by causing small-vessel disease and watershed infarction, which can be its presenting features. Repeated blood tests should be done to rule out HES in central nervous system lesion.

Resolution of a steroid-resistant, hypereosinophilic immune diathesis with mepolizumab and concomitant amelioration of a mixed thrombotic microangiopathy

The anaphylatoxins produced by an unbridled complement cascade in atypical hemolytic uremic syndrome (aHUS) can alter the leukocyte environment in tissues and peripheral blood, causing clinically significant eosinophilia. While the membrane attack complex and C5a anaphlatoxin can be suppressed with anti-C5 biologics, the production of C3a is still capable of driving a destructive hypereosinophilic syndrome in spite of anticomplement therapy. The side-effects of glucocorticoids in treating hypereosinophilic syndrome limit their therapeutic index in long-term treatment and this behooves the use of alternative strategies. While use of the anti-IL-5 antibody, mepolizumab, has been reported for treatment of primary hypereosinophilic syndromes off-label, its usage in the setting of complement-driven thrombotic microangiopathy has not been attempted. We report mepolizumab's rapid resolution of a glucocorticoid-resistant hypereosinophilic syndrome that caused multi-organ dysfunction in a patient with a complex immune diathesis. The patient's long standing TTP/aHUS disease activity, shown to have direct correlation with his eosinophil count, improved with anti-IL-5 therapy, suggesting a reciprocal enhancement between the conditions.

Drug reaction with eosinophilia and systemic symptoms (DRESS syndrome)

OBJECTIVE

To review the hypersensitivity reaction to drugs known as drug reaction with eosinophilia and systemic symptoms (DRESS syndrome), based on a case report. We also intend to discuss the difficulty and importance of disease recognition, since none of the changes is pathognomonic of this disease and failure to identify it may have disastrous consequences for the patient.

METHOD

To describe this case report, in addition to the information collected for clinical assessment, a literature review was performed in the PubMed and Bireme databases in order to retrieve the latest information published in literature on DRESS syndrome.

RESULTS

The case of a 20-year old patient is reported. After anamnesis, physical examination and laboratory tests a diagnosis of DRESS syndrome was performed, characterized by rash, hematologic alterations, lymphadenopathy and lesions in target organ. This is a rare syndrome, whose frequency varies according to the drug used and the immune status of the patient, being more often associated with the use of anticonvulsants.

CONCLUSION

The approach and discussion of the topic are of paramount importance, in view of the potential lethality of this treatable syndrome. Recognizing the occurrence of DRESS syndrome and starting treatment as soon as possible is crucial to reduce the risk of mortality and improve prognosis.

Wells syndrome associated with chronic lymphocytic leukemia

Eosinophilic cellulitis or Wells syndrome is an uncommon skin condition of unknown etiology that can occur alone or associated with other conditions. Typically, it presents with recurrent pruritic, erythematous and edematous plaques, but it can also show clinical polymorphism. Besides the cutaneous lesions, patients can experience systemic manifestations like fever, malaise, arthralgia and peripheral blood eosinophilia. We describe a case of this rare syndrome that presented with polymorphic cutaneous lesions associated with a serious systemic disease, which was revealed through the investigation of the cutaneous disease.

MRI-based evidence for myocardial involvement in women with hypereosinophilic syndrome

PURPOSE

The aim of the study was to assess the presence and spectrum of cardiac abnormalities identified by cardiac magnetic resonance (CMR) in women with hypereosinophilic syndrome (HES) of undefined etiology, who present with normal electrocardiography (ECG) and transthoracic echocardiography (TTE) and no history of heart disease.

METHODS

Ten women (mean age, 48 ± 14 years) with HES of undefined etiology, normal ECG and TTE, and no history of heart disease underwent CMR.

RESULTS

CMR showed cardiac abnormalities in 6 subjects. Five patients had nonischemic late gadolinium enhancement (LGE) lesions within the left ventricular (LV) myocardium, and 3 patients demonstrated CMR evidence of myocardial inflammation. The LV ejection fraction was 68.5 ± 5.7%, and the end-diastolic volume index was 62.7 ± 14.7 mL/m(2). The maximum measured blood eosinophil count correlated with LVLGE volume (r = 0.80, P = 0.006) and was 11374 ± 6242 cells/μL and 4114 ± 2972 cells/μL (P = 0.047) in patients with and without LGE lesions, respectively. The actual blood eosinophil count in subjects with and without CMR evidence of myocarditis was 1058 ± 520 cells/μL and 354 ± 377 cells/μL (P = 0.04), respectively.

CONCLUSIONS

Despite normal ECG, TTE, and absence of history of heart disease, women with HES of unknown etiology frequently demonstrate cardiac abnormalities on CMR, the presence and extent of which are related to blood eosinophil count.

Recurrent severe acute hepatitis caused by hypereosinophilic syndrome associated with elevated serum immunoglobulin G4 levels

A 46-year-old male was admitted to our hospital with severe acute hepatitis, hypereosinophilia, and serum immunoglobulin G4 (IgG4) elevation. Plasma exchange was performed, and he was treated by prednisolone; however, his hepatitis recurred twice over the following twelve months. Transjuglar liver biopsy was performed at the third onset, which demonstrated extensive hepatocyte necrosis, congestion, and severe eosinophil infiltration. We diagnosed hypereosinophilic syndrome (HES)-related hepatitis. Although no cholangitis was detected by imaging and pathological diagnosis, IgG4-positive cells were detected in the liver and bone marrow. Furthermore, the elevation of serum IgG4 levels was associated with the eosinophil count and his clinical condition. After the addition of azathioprine to his treatment regimen, no reoccurrence was observed. IgG4-positive cells may have contributed to the severity and refractoriness of this recurrent acute HES-related hepatitis.

FIP1L1-PDGFRA-Positive Chronic Eosinophilic Leukemia: A Low-Burden Disease with Dramatic Response to Imatinib - A Report of 5 Cases from South India

Objective: Eosinophilia associated with FIP1L1-PDGFRA rearrangement represents a subset of chronic eosinophilic leukemia and affected patients are sensitive to imatinib treatment. This study was undertaken to learn the prevalence and associated clinicopathologic and genetic features of FIP1L1-PDGFRA rearrangement in a cohort of 26 adult patients presenting with profound eosinophilia (>1.5x10⁹/L).

Materials and Methods: Reverse-transcriptase polymerase chain reaction and gel electrophoresis were used for the detection of FIP1L1-PDGFRA rearrangement.

Results: Five male patients with splenomegaly carried the FIP1L1-PDGFRA gene rearrangement. All patients achieved complete hematological response within 4 weeks of starting imatinib. One patient had previous deep vein thrombosis and 1 patient had cardiomyopathy, which improved with steroids and imatinib. Conventional cytogenetics was normal in all these patients. No primary resistance to imatinib was noted.

Conclusion: This study indicates the need to do the FIP1L1-PDGFRA assay in patients with hypereosinophilic syndrome. Prompt treatment of this condition with imatinib can lead to complete hematological response and resolution of the organ damage that can be seen in this setting.

Mitochondria in the center of human eosinophil apoptosis and survival

Eosinophils are abundantly present in most phenotypes of asthma and they contribute to the maintenance and exacerbations of the disease. Regulators of eosinophil longevity play critical roles in determining whether eosinophils accumulate into the airways of asthmatics. Several cytokines enhance eosinophil survival promoting eosinophilic airway inflammation while for example glucocorticoids, the most important anti-inflammatory drugs used to treat asthma, promote the intrinsic pathway of eosinophil apoptosis and by this mechanism contribute to the resolution of eosinophilic airway inflammation. Mitochondria seem to play central roles in both intrinsic mitochondrion-centered and extrinsic receptor-mediated pathways of apoptosis in eosinophils. Mitochondria may also be important for survival signalling. In addition to glucocorticoids, another important agent that regulates human eosinophil longevity via mitochondrial route is nitric oxide, which is present in increased amounts in the airways of asthmatics. Nitric oxide seems to be able to trigger both survival and apoptosis in eosinophils. This review discusses the current evidence of the mechanisms of induced eosinophil apoptosis and survival focusing on the role of mitochondria and clinically relevant stimulants, such as glucocorticoids and nitric oxide.

Regulation of spontaneous eosinophil apoptosis-a neglected area of importance

Asthma is characterized by the accumulation of eosinophils in the airways in most phenotypes. Eosinophils are inflammatory cells that require an external survival-prolonging stimulus such as granulocyte macrophage-colony-stimulating factor (GM-CSF), interleukin (IL)-5, or IL-3 for survival. In their absence, eosinophils are programmed to die by spontaneous apoptosis in a few days. Eosinophil apoptosis can be accelerated by Fas ligation or by pharmacological agents such as glucocorticoids. Evidence exists for the relevance of these survival-prolonging and pro-apoptotic agents in the regulation of eosinophilic inflammation in inflamed airways. Much less is known about the physiological significance and mechanisms of spontaneous eosinophil apoptosis even though it forms the basis of regulation of eosinophil longevity by pathophysiological factors and pharmacological agents. This review concentrates on discussing the mechanisms of spontaneous eosinophil apoptosis compared to those of glucocorticoid- and Fas-induced apoptosis. We aim to answer the question whether the external apoptotic stimuli only augment the ongoing pathway of spontaneous apoptosis or truly activate a specific pathway.

The consequences of not having eosinophils

Several lines of evidence suggest that deficiency of eosinophils is not associated with any characteristic abnormality. Patients lacking eosinophils, in the setting of immunodeficiency or as a consequence of IgG-mediated eosinophil precursor destruction, do not display any distinguishing abnormalities related to eosinophil reduction. The observation that eosinophil-deficient mice do not display any distinctive syndrome or failure of their health is evidence that, under ordinary laboratory conditions, the eosinophil does not play a critical role in the well-being of mammals. Observations that monoclonal antibodies to interleukin-5 (IL-5) are well tolerated appear unsurprising in light of these findings. For example, patients with the hypereosinophilic syndrome have received mepolizumab, an anti-IL-5 monoclonal antibody, for as long as 6 years and have not developed any characteristic set of adverse events. Safety data for reslizumab, another anti-IL-5 monoclonal antibody, and benralizumab, a monoclonal antibody to the IL-5 receptor α-chain, are comparatively limited, especially for benralizumab, although reports of administration of these antibodies to humans suggest that they are well tolerated. Thus, data to the present suggest that reduction of eosinophils appears to have no characteristic ill effects on normal health, and monoclonal antibodies that deplete eosinophils have the potential to be widely employed in the treatment of eosinophil-associated diseases.

Oncostatin M is a FIP1L1/PDGFRA-dependent mediator of cytokine production in chronic eosinophilic leukemia

BACKGROUND

Chronic eosinophilic leukemia (CEL) is a myeloproliferative neoplasm characterized by expansion of neoplastic eosinophils, tissue infiltration, and organ damage. In a subset of these patients, the FIP1L1/PDGFRA (F/P) oncoprotein is detectable. F/P exhibits constitutive tyrosine kinase activity and activates a number of signaling pathways. So far, however, little is known about the role of F/P-dependent proteins in the pathogenesis of CEL.

METHODS

A screen for F/P-dependent cytokines was performed in growth factor-dependent human cell lines lentivirally transduced with F/P. Signal transduction pathways were characterized in Ba/F3 cells with doxycycline-inducible expression of F/P and in EOL-1 cells. Cytokine expression was confirmed in patients' material by immunohistochemistry, immunofluorescence, and confocal microscopy. Gene expression analysis, proliferation assays, and chemotaxis assays were used to elucidate paracrine interactions between neoplastic eosinophils and stromal cells.

RESULTS

We show that F/P upregulates expression of oncostatin M (OSM) in various cell line models in a STAT5-dependent manner. Correspondingly, neoplastic eosinophils in the bone marrow were found to overexpress OSM. OSM derived from F/P + cells stimulated proliferation of stromal cells. Moreover, OSM-containing supernatants from F/P + cells were found to upregulate production of stromal cell-derived factor-1 (SDF-1)/CXCL12 in human fibroblasts. SDF-1, in turn, induced migration of EOL-1 cells in a dose-dependent manner.

CONCLUSIONS

We have identified a F/P-driven paracrine interaction between neoplastic eosinophils and stromal cells that may contribute to tissue fibrosis and accumulation of neoplastic eosinophils in CEL.

Severe eosinophilia in children: a diagnostic dilemma

The differential diagnosis of hypereosinophilia includes both primary (clonal and idiopathic) and secondary medical conditions. Here we raise the awareness of physicians to the unusual causes of hypereosinophilic states and describe the molecular assays used in the diagnosis of hypereosinophilia. Two unusual cases of hypereosinophilia in children that were initially misdiagnosed are reported. T-cell receptor gene rearrangement, skewed X inactivation, fluorescence in situ hybridization analysis, and chromosomal karyotyping were used to reach the final correct diagnosis. Both patients displayed significant eosinophilia and were initially misdiagnosed as having parasitic infection. Nonspecific T-cell clonal expansion was diagnosed in 1 patient based on the clonality of the T-cell receptor variable γ-chain and the skewed chromosome inactivation. The second patient was diagnosed with B-lineage acute lymphoblastic leukemia with a translocation (5;14) (q13;q32) that is well known to be associated with hypereosinophilia. The level of awareness to clonal expansion of WBC subsets which can cause hypereosinophilia should be high when evaluating a patient with extreme eosinophilia. Advanced molecular assays to detect clonal expansion should be used to exclude aberrant clonal processes in such patients.

Mimics of cutaneous lymphoma: report of the 2011 Society for Hematopathology/European Association for Haematopathology workshop

The Society for Hematopathology and European Association for Haematopathology workshop, from October 27 to 29, 2011, in Los Angeles, CA, exhibited many exemplary skin biopsy specimens with interesting inflammatory changes mimicking features of cutaneous lymphoma. This article reviews features observed in cutaneous lymphoid hyperplasia, cutaneous drug reactions, lupus-associated panniculitis, pityriasis lichenoides, hypereosinophilic syndrome, histiocytic necrotizing lymphadenitis, traumatic ulcerative granuloma with stromal eosinophils, and pigmented purpuric dermatosis, as well as a brief review of the pertinent literature and discussion of submitted conference cases. For the pathologist, it is important to be aware of diagnostic pitfalls as well as the limitations of ancillary testing (eg, clonality studies). Finally, correlation with total clinical information, good communication with clinical colleagues, close clinical follow-up with rebiopsy, and prudent use of laboratory studies are vital and will likely offer the best path toward a correct diagnosis.

Clinical overview of cutaneous features in hypereosinophilic syndrome

The hypereosinophilic syndromes (HES) are a heterogeneous group of disorders defined as persistent and marked blood eosinophilia of unknown origin with systemic organ involvement. HES is a potentially severe multisystem disease associated with considerable morbidity. Skin involvement and cutaneous findings frequently can be seen in those patients. Skin symptoms consist of angioedema; unusual urticarial lesions; and eczematous, therapy-resistant, pruriginous papules and nodules. They may be the only obvious clinical symptoms. Cutaneous features can give an important hint to the diagnosis of this rare and often severe illness. Based on advances in molecular and genetic diagnostic techniques and on increasing experience with characteristic clinical features and prognostic markers, therapy has changed radically. Current therapies include corticosteroids, hydroxyurea, interferon-α, the tyrosine kinase inhibitor imatinib mesylate, and (in progress) the monoclonal anti-interleukin-5 antibodies. This article provides an overview of current concepts of disease classification, different skin findings, and therapy for HES.

Diagnostic Complexities of Eosinophilia

Context.— The advent of molecular tools capable of subclassifying eosinophilia has changed the diagnostic and clinical approach to what was classically called hypereosinophilic syndrome.

Objectives.— To review the etiologies of eosinophilia and to describe the current diagnostic approach to this abnormality.

Data Sources.— Literature review.

Conclusions.— Eosinophilia is a common, hematologic abnormality with diverse etiologies. The underlying causes can be broadly divided into reactive, clonal, and idiopathic. Classically, many cases of eosinophilia were grouped together into the umbrella category of hypereosinophilic syndrome, a clinical diagnosis of exclusion. In recent years, an improved mechanistic understanding of many eosinophilias has revolutionized the way these disorders are understood, diagnosed, and treated. As a result, specific diagnoses can now be assigned in many cases that were previously defined as hypereosinophilic syndrome. Most notably, chromosomal rearrangements, such as FIP1L1-PDGFRA fusions caused by internal deletions in chromosome 4, are now known to be associated with many chronic eosinophilic leukemias. When present, these specific molecular abnormalities predict response to directed therapies. Although an improved molecular understanding is revolutionizing the treatment of patients with rare causes of eosinophilia, it has also complicated the approach to evaluating and treating eosinophilia. Here, we review causes of eosinophilia and present a framework by which the practicing pathologist may approach this diagnostic dilemma. Finally, we consider recent cases as clinical examples of eosinophilia from a single institution, demonstrating the diversity of etiologies that must be considered.

[Myeloproliferative hypereosinophilic syndrome revealed by bipolar mucosal ulcerations]

BACKGROUND

Hypereosinophilic syndrome (HES) is defined as an eosinophil count equal to or greater than 1.5 G/L for more than 6 months with organ damage (heart, nervous system, lung, etc) after the exclusion of other common causes of eosinophilia. A myeloproliferative variant of HES with FIP1L1-PDGFRα fusion gene inducing constitutive activation of a tyrosine kinase receptor has been characterized. We report a case in which the diagnosis was revealed by mucosal erosions and ulcerations.

PATIENTS AND METHODS

A 50-year-old man reported bipolar erosions. He presented with an erosion on the glans, an ulceration on the lower lip and mild dermographism. He had an eosinophil count of 7.5 G/L (n<0.7) and raised LDH at 520 IU/L (n<480). Screening for the usual causes of eosinophilia was negative. Histology of the labial ulceration showed a polymorphous inflammatory infiltrate containing eosinophils. A chest scan demonstrated a ground glass-like pulmonary infiltrate and broncho-alveolar lavage revealed eosinophilic alveolitis. The myelogram showed rich bone marrow with eosinophils. FIP1L1-PDGFRα fusion transcript was detected in the blood. Imatinib (Glivec(®)) was initiated and a favourable outcome was achieved within a few months and maintained after one year of treatment.

DISCUSSION

Cutaneous signs are frequent features of HES. They are polymorphous and include pruritis, erythematous rash and urticaria. Mucosal ulcerations are uncommon and appear more frequently with the myeloproliferative FIP1L1-PDGFRα-associated variant of HES. Early diagnosis allows the onset of a targeted treatment with imatinib that may prevent the apparition of organ damage.

High-risk ALK negative anaplastic large-cell lymphoma presenting with hypereosinophilic syndrome in a 2.5-year-old child

The hypereosinophilic syndromes (HES) are characterized by prolonged nonreactive peripheral blood hypereosinophilia with tissue damage. The lymphocytic HES variant can precede malignant clonal T-cell disease in adults but it is extremely rare to be the presenting feature of lymphomas in children. Here we present a 2.5-year-old boy with HES and mediastinal T-cell anaplastic lymphoma kinase (ALK) negative systemic anaplastic large-cell lymphoma. Mature and immature eosinophils without blasts were shown on bone marrow aspiration while biopsy revealed malignant infiltration. The patient responded well to initial corticosteroid therapy, but high-risk features make a challenge of finding the cure in this extremely rare case.

Synovial fluid eosinophilia: a case series with a long follow-up and literature review

OBJECTIVES

To establish the frequency and describe the characteristics of a cohort of patients with SF eosinophilia (SFE) and a long clinical follow-up. A systematic review of the literature on this topic was performed.

METHODS

From November 2005 to May 2010, 982 consecutive arthrocentesis procedures performed at a tertiary care hospital were reviewed. Clinical and analytical data of patients with SFE at the time of diagnosis and during follow-up until 31 January 2012, were recorded. According to the percentage of eosinophils in SF, SFE was classified as minor (<10%) or major (>10%). Also, a literature search of all publications on eosinophilic synovitis found in MEDLINE, EMBASE and Web of Science without publication date restrictions was performed.

RESULTS

Eosinophils in SF were found in 10 of 982 (1.02%) patients: minor SFE was recorded in three patients, all of them with haemorrhagic fluid and without peripheral eosinophilia. Major SFE was found in seven patients, and only two of them had peripheral eosinophilia. In six patients, an underlying cause of the arthritis was found. Only one patient was classified as having idiopathic SFE. Most SFE promptly resolved with NSAIDs without relapses or new deformities. The literature search identified 56 patients with SFE; 49 of them (88%) had major SFE and 7 (12%) had minor SFE.

CONCLUSIONS

Eosinophils are infrequently found in SF, and in most cases peripheral eosinophilia was not detected. Most patients with SFE had a benign course with prompt resolution and few relapses.

Hypereosinophilia: more than meets the eye

INTRODUCTION

Eosinophilia has myriad causes and is occaisonally seen in association with malignancies. Acute myeloid leukemia presenting with eosinophilia has rarely been reported in children.

CASE

Authors herein present a case of a 5-year-old boy who presented with marked peripheral eosinophilia with symptoms of organ infiltration. Extensive work-up was needed before the diagnosis was established in this patient.

DISCUSSION

Through this case report, we want to emphasize that peripheral eosinophilia could be a dilemma challenging clinical skills and often needing vigorous perusal for the diagnosis.

Spontaneous resolution of hypereosinophilic syndrome in an infant without treatment

We report on a 4-month-old boy with hypereosinophilic syndrome (HES) and spontaneous progressive resolution without treatment. Differential diagnosis excluded myeloproliferative, lymphocytic, familiar, associated, and overlap HES. The final diagnosis was undefined HES. Repeated measurements of blood eosinophil counts, monitoring of clonal T cells, and observation of skin lesions and organ involvement were carefully performed as an outpatient.

Response to imatinib mesylate in patients with hypereosinophilic syndrome

Idiopathic hypereosinophilic syndrome (HES) is a rare disorder characterized by unexplained, persistent hypereosinophilia associated with multiple organ dysfunctions. The cause of HES is unknown and shows clinical heterogeneity. FIP1L1-PDGFRA fusion is a clonal marker for the diagnosis and treatment of HES. We prospectively studied 78 patients with chronic eosinophilia. In all cases, the most salient clinical and biological characteristics as well as the response to the therapy were analyzed. In addition, we performed conventional cytogenetics and fluorescent in situ hybridization (FISH) with three BACs covering the FIP1-like-1 (FIP1L1)/platelet-derived growth factor receptor-α gene (PDGFRA) fusion. Nineteen of 78 patients (24 %) presented criteria of HES. The majority of patients were male (18) with median age of 49 years (range 19-84 years). FIP1L1-PDGFRA fusion was found in eight patients. Patients with FIP1L1-PDGFRA fusion presented with more bone marrow eosinophils and peripheral blood eosinophilia as well as anemia, leukocytosis and thrombocytopenia. Using of low-dose imatinib mesylate (100 mg/day) a hematological and molecular remission in all patients displaying the FIP1L1-PDGFRA fusion gene was observed. Therefore, imatinib may be effective for use in the treatment of chronic eosinophilic leukemia, and patients should be treated before tissue damage.

NIK prevents the development of hypereosinophilic syndrome-like disease in mice independent of IKKα activation

Immune cell-mediated tissue injury is a common feature of different inflammatory diseases, yet the pathogenetic mechanisms and cell types involved vary significantly. Hypereosinophilic syndrome (HES) represents a group of inflammatory diseases that is characterized by increased numbers of pathogenic eosinophilic granulocytes in the peripheral blood and diverse organs. On the basis of clinical and laboratory findings, various forms of HES have been defined, yet the molecular mechanism and potential signaling pathways that drive eosinophil expansion remain largely unknown. In this study, we show that mice deficient of the serine/threonine-specific protein kinase NF-κB-inducing kinase (NIK) develop a HES-like disease, reflected by progressive blood and tissue eosinophilia, tissue injury, and premature death at around 25-30 wk of age. Similar to the lymphocytic form of HES, CD4(+) T cells from NIK-deficient mice express increased levels of Th2-associated cytokines, and eosinophilia and survival of NIK-deficient mice could be prevented completely by genetic ablation of CD4(+) T cells. Experiments based on bone marrow chimeric mice, however, demonstrated that inflammation in NIK-deficient mice depended on radiation-resistant tissues, implicating that NIK-deficient immune cells mediate inflammation in a nonautonomous manner. Surprisingly, disease development was independent of NIK's known function as an IκB kinase α (IKKα) kinase, because mice carrying a mutation in the activation loop of IKKα, which is phosphorylated by NIK, did not develop inflammatory disease. Our data show that NIK activity in nonhematopoietic cells controls Th2 cell development and prevents eosinophil-driven inflammatory disease, most likely using a signaling pathway that operates independent of the known NIK substrate IKKα.

Contemporary consensus proposal on criteria and classification of eosinophilic disorders and related syndromes

Eosinophilia is an important indicator of various neoplastic and nonneoplastic conditions. Depending on the underlying disease and mechanisms, eosinophil infiltration can lead to organ dysfunction, clinical symptoms, or both. During the past 2 decades, several different classifications of eosinophilic disorders and related syndromes have been proposed in various fields of medicine. Although criteria and definitions are, in part, overlapping, no global consensus has been presented to date. The Year 2011 Working Conference on Eosinophil Disorders and Syndromes was organized to update and refine the criteria and definitions for eosinophilic disorders and to merge prior classifications in a contemporary multidisciplinary schema. A panel of experts from the fields of immunology, allergy, hematology, and pathology contributed to this project. The expert group agreed on unifying terminologies and criteria and a classification that delineates various forms of hypereosinophilia, including primary and secondary variants based on specific hematologic and immunologic conditions, and various forms of the hypereosinophilic syndrome. For patients in whom no underlying disease or hypereosinophilic syndrome is found, the term hypereosinophilia of undetermined significance is introduced. The proposed novel criteria, definitions, and terminologies should assist in daily practice, as well as in the preparation and conduct of clinical trials.

Hypereosinophilic syndrome associated with simultaneous intracardiac thrombi, cerebral thromboembolism and pulmonary embolism

The hypereosinophilic syndrome (HES) is a subcategory of idiopathic eosinophilia which is characterized by marked unexplained eosinophilia and evidence of tissue eosinophilia which leads to eosinophil-mediated organ damage. Cardiac and thromboembolic complications of HES are the common causes of mortality and morbidity. Here, we report a 54-year-old woman with HES who presented with simultaneously occurring cardiac thrombi, pulmonary embolism, and cerebrovascular thromboembolism.

Steroid-unresponsive hypereosinophilic syndrome

Hypereosinophilic syndrome in children is rare and is characterised by sustained over-production of eosinophils. An 11-year-old boy was diagnosed with hypereosinophilic syndrome as per standard criteria. He was treated initially with intravenous methylprednisolone, followed by oral prednisolone, to which he showed a limited response. The highest absolute eosinophil count was 27.0×10(9)/L. He was commenced on imatinib mesylate but, because of no response, he was switched to hydroxyurea combined with low-dose prednisolone to which he showed improvement with decreasing levels of eosinophils.

Mepolizumab in eosinophilic disorders

Mepolizumab (Bosatria(®), GlaxoSmithKline) is a biologic agent developed to treat asthma. It represents a humanized monoclonal antibody of IgG1 κ type, which targets human IL-5 and thus prevents its interaction with the α-chain of the IL-5 receptor. To date, it has not been approved for use in any eosinophil-related disorder; however, several studies have suggested some therapeutic benefit across a spectrum of eosinophil-related disorders. This article evaluates the currently available preclinical and clinical studies, and the impact of mepolizumab against a variety of eosinophilic disorders.

Molecular and clinical rationale for therapeutic targeting of interleukin-5 and its receptor

Interleukin-5 is a Th2 homodimeric cytokine involved in the differentiation, maturation, migration, development, survival, trafficking and effector function of blood and local tissue eosinophils, in addition to basophils and mast cells. The IL-5 receptor (IL-5R) consists of an IL-5-specific α subunit that interacts in conformationally dynamic ways with the receptor's βc subunit, an aggregate of domains it shares with binding sites of IL-3 and granulocyte-macrophage colony-stimulating factor. IL-5 and IL-5R drive allergic and inflammatory immune responses characterizing numerous diseases, such as asthma, atopic dermatitis, chronic obstructive pulmonary disease, eosinophilic gastrointestinal diseases, hyper-eosinophilic syndrome, Churg-Strauss syndrome and eosinophilic nasal polyposis. Although corticosteroid therapy is the primary treatment for these diseases, a substantial number of patients exhibit incomplete responses and suffer side-effects. Two monoclonal antibodies have been designed to neutralize IL-5 (mepolizumab and reslizumab). Both antibodies have demonstrated the ability to reduce blood and tissue eosinophil counts. One additional monoclonal antibody, benralizumab (MEDI-563), has been developed to target IL-5R and attenuate eosinophilia through antibody-dependent cellular cytotoxicity. All three monoclonal antibodies are being clinically evaluated. Antisense oligonucleotide technology targeting the common βc IL-5R subunit is also being used therapeutically to inhibit IL-5-mediated effects (TPI ASM8). Small interfering RNA technology has also been used therapeutically to inhibit the expression of IL-5 in animal models. This review summarizes the structural interactions between IL-5 and IL-5R and the functional consequences of such interactions, and describes the pre-clinical and clinical evidence supporting IL-5R as a therapeutic target.

Histopathologic diagnosis of eosinophilic conditions in the gastrointestinal tract

Eosinophils, a constitutive component of the columnar-lined gastrointestinal tract, play an essential role in allergic responses and parasitic infections. The tissue density of these cells also increases in a variety of conditions of uncertain etiology. With the exception of the esophageal squamous epithelium, in which no eosinophils are normally present, the population of normal eosinophils in the remainder of the luminal gut is poorly defined. Therefore, histopathologists must rely on their subjective judgment to determine when a diagnosis of eosinophilic gastritis, enteritis, or colitis should be rendered. Eosinophilic esophagitis is currently the best defined and most studied eosinophilic condition of the digestive tract; therefore, the confidence in accurate diagnosis is increasing. In contrast, the characteristic clinicopathologic features of eosinophilic conditions affecting other parts of the digestive tract remain somewhat elusive. This review was designed to present pathologists with simple and practical information for the biopsy-based histopathologic diagnosis of eosinophilic esophagitis, gastritis, enteritis, and colitis. It was prepared by critically reviewing more than 200 articles on the topic, along with incorporating evidence accumulated through our own collective experience. We anticipate that by increasing pathologists' confidence in reporting these abnormal but often nameless eosinophilic infiltrates, we can help better define and characterize their significance.