Clinical characteristics and outcome of pediatric patients diagnosed with Langerhans cell histiocytosis in pediatric hematology and oncology centers in Poland

Abstract Background Langerhans cell histiocytosis (LCH) affects 1–2 in 1,000,000 people. The disease is not associated with increased risk of treatment failure (especially among older children), but appropriate procedures implemented in advance can eliminate complications which might appear and significantly worsen the patients’ quality of life. Thus, we sought to evaluate the clinical features, management, and outcome of children with LCH treated in Polish pediatric hematology-oncology centers. Materials and methods One hundred eighty two patients with LCH were treated according to the Histiocytic Society Guidelines between 2010 and 2017. The participating centers were requested to provide the following data: demographic, clinical, as well as local or systemic treatment data and patients’ outcome. Overall survival (OS) and event free survival (EFS) were estimated by Kaplan-Meier methods and compared using the log-rank test. Results Sixty nine percent of children were classified as single system (SS). The patients with SS disease were significantly older as compared to the children with multisystem disease (MS), 6 vs. 2.3 years respectively (p 0.003). Bones were involved in 76% of patients. Systemic treatment was applied to 47% of children with SS disease and 98% with MS disease. Fourteen patients relapsed while two children died. OS and EFS in entire group were 0.99 and 0.91 respectively (with median follow-up 4.3 years). Conclusion The treatment of LCH in Polish centers was effective, however, new approaches, including mutation analyses and good inter-center cooperation, are needed to identify patients who might require modification or intensification of treatment.

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BRAFV600E frequency and impact on outcomes in adults with langerhans cell histiocytosis.

Journal of Clinical Oncology ◽

10.1200/jco.2021.39.15_suppl.7050 ◽

2021 ◽

Vol 39 (15_suppl) ◽

pp. 7050-7050

Author(s):

Aldo A. Acosta-Medina ◽

Jithma P. Abeykoon ◽

N. Nora Bennani ◽

Caroline Davidge-Pitts ◽

Matthew J. Koster ◽

...

Keyword(s):

Langerhans Cell Histiocytosis ◽

Disease Risk ◽

Clinical Manifestations ◽

Braf Inhibitor ◽

Progression Free Survival ◽

Langerhans Cell ◽

Rank Test ◽

Multisystem Disease ◽

Mutational Status ◽

Increased Risk

7050 Background: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm manifesting as unifocal, multifocal, multisystem (MS) or pulmonary LCH (smoking-related). In pediatric LCH, somatic BRAFV600E prevalence is reported at 55-70%, and associated with increased risk of multisystem disease and early treatment failure. Our aim was to describe the prevalence of BRAFV600E mutation and evaluate its association with clinical manifestations and outcomes in adults with LCH. Methods: A retrospective review of adult patients diagnosed with LCH consecutively seen at Mayo Clinic from 2011 to 2020 was performed.Evaluation of association of BRAFV600E mutational status and clinical factors was conducted by the Chi-square test for independence. Progression-free survival (PFS) and overall survival (OS) were analyzed via the Kaplan Meier method and compared with the log-rank test to assess the effect of BRAFV600E. Results: Of the total LCH cohort ( n= 128), 88 patients with available BRAFV600E results were included in the study. Median age at diagnosis was 41y (range 19 - 88); 52.3% were male. 40 (45.5%) patients had a BRAFV600E mutation. Increasing age was associated with BRAFV600E (10-year increase OR 1.42, 95%CI 1.07-1.89; p= 0.017). No correlation was observed between BRAFV600E status and site of disease, risk organ (RO: liver, spleen, marrow) involvement, or MS disease. Patients with BRAFV600E were 4 times more likely to receive targeted therapy ( BRAF inhibitor) than non- BRAFV600E patients ( p= 0.018). After a median follow up of 46 mo (95% CI 30.8-61.2), PFS was similar between BRAFV600E and non- BRAFV600E patients ( p= 0.167). However, patients with BRAFV600E had a worse 3-year OS compared with non- BRAFV600E patients (84% vs. 97.1%, p= 0.027). Patients who died had a significantly higher age at LCH diagnosis (median 62 vs. 38 years; p= 0.0002). Conclusions: In our cohort of adults with LCH, BRAFV600E was less frequent than reported in pediatric literature and was associated with worse OS. The frequency of BRAFV600E was positively correlated with increasing age. Contrary to reports in pediatric LCH, there were no significant associations between BRAFV600E and high-risk or multisystem disease.[Table: see text]

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Paediatric Langerhans Cell Histiocytosis Disease: Long-Term Sequelae in the Hypothalamic Endocrine System

Hormone Research in Paediatrics ◽

10.1159/000517040 ◽

2021 ◽

pp. 1-9

Author(s):

Elisa Vaiani ◽

Guido Felizzia ◽

Fabiana Lubieniecki ◽

Jorge Braier ◽

Alicia Belgorosky

Keyword(s):

Anterior Pituitary ◽

Langerhans Cell Histiocytosis ◽

Endocrine System ◽

Langerhans Cell ◽

Hormone Deficiency ◽

Bone Lesions ◽

Pituitary Hormone ◽

Multisystem Disease ◽

Anterior Pituitary Hormone

Langerhans cell histiocytosis (LCH) is a disorder of the mononuclear phagocyte system that can affect almost any organ and system. The most common central nervous system (CNS) manifestation in LCH is the infiltration of the hypothalamic-pituitary region leading to destruction and neurodegeneration of CNS tissue. The latter causes the most frequent endocrinological manifestation, that is, central diabetes insipidus (CDI), and less often anterior pituitary hormone deficiency (APD). The reported incidence of CDI is estimated between 11.5 and 24% and is considered a risk factor for neurodegenerative disease and APD. Three risk factors for development of CDI are recognized in the majority of the studies: (1) multisystem disease, (2) the occurrence of reactivations or active disease for a prolonged period, and (3) the presence of craniofacial bone lesions. Since CDI may occur as the first manifestation of LCH, differential diagnosis of malignant diseases like germ cell tumours must be made. APD is almost always associated with CDI and can appear several years after the diagnosis of CDI. Growth hormone is the most commonly affected anterior pituitary hormone. Despite significant advances in the knowledge of LCH in recent years, little progress has been made in preventing long-term sequelae such as those affecting the hypothalamic-pituitary system.

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Adult-onset Neurological Langerhans Cell histiocytosis and Response to Treatment

Austin Journal of Clinical Neurology ◽

10.26420/austinjclinneurol.2021.1146 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Al-Hader R ◽

◽

Suneja A ◽

Memon AB ◽

Mukherje A ◽

...

Keyword(s):

Langerhans Cell Histiocytosis ◽

Brain Magnetic Resonance Imaging ◽

Langerhans Cell ◽

Response To Therapy ◽

Response To Treatment ◽

Adult Onset ◽

Multisystem Disease ◽

Clonal Proliferation ◽

Magnetic Resonance Imaging Mri ◽

Mass Lesions

Introduction: Langerhans Cell Histiocytosis (LCH) is a rare form of cancer that mostly affects children and rarely adults. LCH involves an abnormal clonal proliferation of Langerhans cells in the bone marrow. These cells are capable of migrating from the skin to lymph nodes. Therefore, it is characterized as a multisystem disease. Neurological manifestations are not common, and often patients’ present with endocrine dysfunction with neuroimaging findings of hypothalamic and pituitary masses can mimic pituitary adenoma. Here, we discuss two instances of unusual adult-onset, primary neurological LCH in patients with a positive response to therapy-these two patients presented with mass lesion and neurodegenerative form of LCH, respectively. LCH can manifest features of mass lesions or neurodegeneration on brain Magnetic Resonance Imaging (MRI). Since it is rare in adults, it is crucial to identify this condition as timely treatment can have a better prognosis.

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Childhood Langerhans cell histiocytosis with severe lung involvement: a nationwide cohort study

Orphanet Journal of Rare Diseases ◽

10.1186/s13023-020-01495-5 ◽

2020 ◽

Vol 15 (1) ◽

Author(s):

Solenne Le Louet ◽

Mohamed-Aziz Barkaoui ◽

Jean Miron ◽

Claire Galambrun ◽

Nathalie Aladjidi ◽

...

Keyword(s):

Targeted Therapy ◽

Langerhans Cell Histiocytosis ◽

Treatment Guidelines ◽

Langerhans Cell ◽

Infection Prophylaxis ◽

Lung Involvement ◽

Multisystem Disease ◽

Abnormal Chest ◽

Life Threatening ◽

Severe Lung

Abstract Background Lung involvement in childhood Langerhans cell histiocytosis (LCH) is infrequent and rarely life threatening, but occasionally, severe presentations are observed. Methods Among 1482 children (< 15 years) registered in the French LCH registry (1994–2018), 111 (7.4%) had lung involvement. This retrospective study included data for 17 (1.1%) patients that required one or more intensive care unit (ICU) admissions for respiratory failure. Results The median age was 1.3 years at the first ICU hospitalization. Of the 17 patients, 14 presented with lung involvement at the LCH diagnosis, and 7 patients (41%) had concomitant involvement of risk-organ (hematologic, spleen, or liver). Thirty-five ICU hospitalizations were analysed. Among these, 22 (63%) were secondary to a pneumothorax, 5 (14%) were associated with important cystic lesions without pneumothorax, and 8 (23%) included a diffuse micronodular lung infiltration in the context of multisystem disease. First-line vinblastine–corticosteroid combination therapy was administered to 16 patients; 12 patients required a second-line therapy (cladribine: n = 7; etoposide-aracytine: n = 3; targeted therapy n = 2). A total of 6 children (35%) died (repeated pneumothorax: n = 3; diffuse micronodular lung infiltration in the context of multisystem disease: n = 2; following lung transplantation: n = 1). For survivors, the median follow-up after ICU was 11.2 years. Among these, 9 patients remain asymptomatic despite abnormal chest imaging. Conclusions Severe lung involvement is unusual in childhood LCH, but it is associated with high mortality. Treatment guidelines should be improved for this group of patients: viral infection prophylaxis and early administration of a new LCH therapy, such as targeted therapy.

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Langerhans-Cell Histiocytoses - Epidemiology, Classification, Clinical Features, Diagnosis, Complications, Treatment and Prognosis

Journal of Biomedical and Clinical Research ◽

10.1515/jbcr-2016-0001 ◽

2016 ◽

Vol 9 (1) ◽

pp. 3-16 ◽

Cited By ~ 1

Author(s):

Vera E. Papochieva ◽

Dimitrinka S. Miteva ◽

Penka I. Perenovska ◽

Guergana Petrova

Keyword(s):

Langerhans Cell Histiocytosis ◽

Eosinophilic Granuloma ◽

Langerhans Cell ◽

Unknown Etiology ◽

Bone Lesions ◽

Multisystem Disease ◽

The Past ◽

System Disease ◽

Young Smokers ◽

Underlying Pathology

Summary Histiocytoses comprise a group of diverse diseases of unknown etiology with various clinical presentation and evolution. The underlying pathology is characterised by accumulation and infiltration of variable numbers of cells of the monocyte-macrophage line in the affected tissues and organs. Histiocytoses are divided into three major classes: Langerhans cell histiocytosis (LCH), non- Langerhans cell histiocytosis, and malignant histiocytic disorders. The term LCH (also known in the past as histiocytosis X) encompasses the following rare diseases: Eosinophilic Granuloma, Hand-Schuller-Christian disease, Letterer-Siwe disease, Hashimoto-Pritzker disease, in which accumulation of pathologic Langerhans cells (LCs) leads to tissue damage. LCs usually reside in the skin and ensure protection against infections by destroying foreign substances. LC accumulation is caused by antigen stimulation and inadequate immune response. Thus, clinical LCH manifestations range from isolated disease with mono- or multifocal bone lesions to disseminated multisystem disease. LCH is a rare disease, affecting mainly children and young smokers, aged 20-50 years. Lung involvement in LCH usually presents as a mono-system disease and is characterized by Langerhans cell granulomas (LCG) infiltrating and impairing the distal bronchioles. The definite diagnosis is based on lung biopsy of CAT selected LCG areas. So far, there is no an effective treatment, but the better understanding of the mechanisms involved in the pathogenesis of the disease would help in the development of effective therapeutic strategies in the future.

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TNF-α-238GA, IL-1α-889CC and IL-10–819CC Polymorphisms Confere an Increased Risk to Develop Multisystem Langerhans Cell Histiocytosis.

Blood ◽

10.1182/blood.v104.11.1331.1331 ◽

2004 ◽

Vol 104 (11) ◽

pp. 1331-1331

Author(s):

Paola De Filippi ◽

Cesare Danesino ◽

Diego Ferrarese ◽

Annalisa De Silvestri ◽

Carla Badulli ◽

...

Keyword(s):

Langerhans Cell Histiocytosis ◽

Bone Lesion ◽

Multiple Organ ◽

Langerhans Cell ◽

Cytokine Network ◽

Regional Lymph Nodes ◽

Cytokines And Chemokines ◽

Increased Risk ◽

Tnf Α ◽

Disseminated Disease

Abstract Langerhans cell Histiocytosis (LCH) (OMIM 604856) is a rare disorder affecting any age, with a highly variable clinical course, usually related to the number and type of organs affected at the time of presentation. The symptoms range from a solitary bone lesion that does not require treatment to a disseminated disease with multiple-organ involvement and a high mortality rate, despite aggressive treatment. The pathogenesis of LCH remains unclear, although deregulated growth, activity and trafficking of Langerhans cells (LC) are implicated. The ability of LC to migrate from the epidermis to regional lymph nodes is of pivotal importance for the induction of immune response and there is increasing evidence that both cytokines and chemokines are implicated in this function. We report the analysis of polymorphisms in genes coding for different cytokines in a population of patients with LCH in comparison to an Italian control population (n=140). We studied 40 patients, with a mean age at the disease of onset of 6.1 (±5.0) years; the 15 with single-system (SS) disease had a mean age of 7.1 (±3.9) years, while the 25 with multi-system (MS) disease had a mean age of 5.3 (±5.3) years. The Cytokine Genotyping Tray (Pel-Freez, Milwaukee, USA) was used for the detection of the following polymorphisms: Il-1α-889 C/T, Il-1β (−511 C/T; +3962 T/C), IL-1R pst1 1970 C/T, IL-RA mspa1 11100 T/C, IL-4Rα +1902 G/A, IL-12 -1188 C/A, γ IFN UTR 5644 A/T, TNF α (−308 G/A; −238 G/A), IL-2 (−330 T/G; +160 G/T), IL-4 (−1098T/G; −590 T/C; −33 T/C), IL-6 (−174 G/C; nt565 G/A), IL-10 (−1082 G/A; −819 C/T; −592 C/A). The following polymorphisms showed a different distribution in patients versus controls: IL-4–33 (p=0.048); IL-4–590 (p=0.005); IL-1α-889 (p=0.009). The correspondence analysis of these variables showed that genotypes IL-4 -33TT, IL-4 -590 TC and-1β+3962TT confer an increased risk of developing SS disease, while genotypes TNF-α-238GA, IL-1α-889CC and IL-10–819CC give an increased risk of developing MS disease. The present study supports the concept that constitutional variants affecting the cytokine network may induce susceptibility to develop LCH and also affect its manifestations. Figure Figure

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Adult Langerhans cell histiocytosis: A contemporary single-institution series of 186 patients.

Journal of Clinical Oncology ◽

10.1200/jco.2019.37.15_suppl.7018 ◽

2019 ◽

Vol 37 (15_suppl) ◽

pp. 7018-7018

Author(s):

Gaurav Goyal ◽

Marie Hu ◽

Jason R Young ◽

Robert Vassallo ◽

Jay H Ryu ◽

...

Keyword(s):

Smoking Cessation ◽

Langerhans Cell Histiocytosis ◽

Overall Response Rate ◽

Langerhans Cell ◽

Braf V600e ◽

First Line ◽

Multisystem Disease ◽

Presenting Symptoms ◽

Systemic Therapies

7018 Background: Langerhans cell histiocytosis (LCH) is a rare histiocytic neoplasm driven by MAPK-ERK mutations in majority of patients. Contemporary data on treatments and outcomes in adult LCH are lacking. Hence, we undertook this study to analyze a large cohort of adult LCH patients. Methods: This was a retrospective study of adult (≥18 years) LCH patients seen at our institution between 1998 and 2018. Results: We included 186 patients with adult LCH (median age 43; 19-88), and 54% were females. 70% of patients were diagnosed after 2007. Common presenting symptoms were cough/dyspnea (30%), rash (17%), pain/swelling in head (17%), and diabetes insipidus (10%). 70 (38%) patients had multisystem LCH, 62 (33%) had isolated pulmonary LCH, and 35 (19%) had unifocal LCH. Common sites of involvement included lung (59%), bone (37%), skin (21%), and nervous system (16%). 121 (65%) were smokers; 48% of these had lung disease, while 52% had multisystem disease. 18 of 31 tested (58%) patients had BRAF-V600E mutation. Most common first-line treatment was smoking cessation in 24 patients, and led to an overall response rate (ORR) of 83% in pulmonary lesions. Radiation therapy was used in 11 patients, and led to an ORR 82%. Surgical resection of lesion was done in 23 patients, with relapses in 24%. Systemic therapies were used in 78 (42%) patients (Table). Most common first-line systemic therapy was cladribine with ORR of 78%. Vemurafenib was used in 3 patients with BRAF-V600E, leading to an ORR of 67% . After a median follow-up of 23 months (0-261), 21 patients had died. Of these, 10 died of progressive LCH. Median OS was not reached, and mean OS was 196 months. Conclusions: This is the largest contemporary series of adult LCH. It shows that diverse clinical spectrum, ranging from benign course to a progressive multisystem disease. Although smoking cessation was an effective treatment for pulmonary LCH, a large subset required systemic chemotherapy. [Table: see text]

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SURG-34. MULTIDISCIPLINARY MANAGEMENT OF A PATIENT WITH OPTIC PATHWAY-HYPOTHALAMIC LANGERHANS CELL HISTIOCYTOSIS: A CASE REPORT

Neuro-Oncology ◽

10.1093/neuonc/noaa215.880 ◽

2020 ◽

Vol 22 (Supplement_2) ◽

pp. ii210-ii210

Author(s):

John Emmanuel Custodio ◽

Kevin Paul Ferraris ◽

Joseph Erroll Navarro ◽

Kenny Seng ◽

Jose Carlos Alcazaren ◽

...

Keyword(s):

Langerhans Cell Histiocytosis ◽

S100 Protein ◽

Visual Fields ◽

Langerhans Cell ◽

Normal Body Mass Index ◽

Team Approach ◽

Hypothalamic Region ◽

Suprasellar Region ◽

Increased Risk ◽

History Of

Abstract Langerhans cell histiocytosis (LCH) of the Central Nervous System (CNS) is rare. Isolated involvement of the hypothalamic region is much more extremely rare with only 0.04 to 0.6% of the cases. We report a case of a 33 year-old female who presented with a one-year history of amenorrhea and a five-month history of intermittent headache, memory lapse, and somnolence. The patient was of normal body mass index with normal visual acuity and intact visual fields. Laboratory examinations revealed panhypopituitarism with central diabetes insipidus. Cranial magnetic resonance imaging showed a large lobulated mass measuring 1.9 x 2.2 x 2 cm in the suprasellar region which extended to the pituitary infundibulum, hypothalamus and retrochiasmatic region, with surrounding edema. The patient underwent right orbitozygomatic craniotomy and subtotal excision of the mass through subfrontal and transsylvian approaches. Histopathological examination of langerhans cells were observed with positive immunohistochemical stain for CD1a and S100 protein antigen markers establishing a diagnosis of CNS LCH. Thoracoabdominal computed tomography scan and bone scan were done postoperatively and showed no evidence of extracranial lesions. The patient had been receiving prednisone and vinblastine based chemotherapy regimen. She remains to be asymptomatic and on close surveillance. To date, there is no standardized treatment strategy for CNS LCH in the adult population. An accurate histopathologic diagnosis and a specialized multidisciplinary team approach especially involving Oncology, Neurosurgery, Ophthalmology and Endocrinology are critical to optimally tailor possible effective treatment options for patients with this similar disease. Long-term follow-up is crucial due to the increased risk of local recurrence and multisystemic involvement.

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Pediatric Langerhans Cell Histiocytosis (LCH) Clinical Outcome in Hospital Civil De Guadalajara, México

Blood ◽

10.1182/blood-2018-99-115794 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 4951-4951 ◽

Cited By ~ 1

Author(s):

Katterine Rojas Rodríguez ◽

Veronica Soto ◽

Carlos Rodriguez-Galindo ◽

Paola M. Friedrich ◽

Edwin Guzmán ◽

...

Keyword(s):

Clinical Outcome ◽

Langerhans Cell Histiocytosis ◽

Disease Risk ◽

Conflicts Of Interest ◽

Systemic Disease ◽

Giant Cells ◽

Langerhans Cell ◽

Induction Treatment ◽

Multisystem Disease ◽

Clonal Proliferation

Abstract Pediatric Langerhans cell histiocytosis (LCH) clinical outcome in Hospital Civil de Guadalajara, México. Introduction : LCH results from clonal proliferation of functionally and immunophenotyped inmature round Langerhans cells along with eosinophiles, machrophages, lymphocytes and ocasionally multinucleated giant cells (1). Its incidence is 2-10 cases by million of children below 15 yr in US (2). Our objective was to describe the clinical characteristics and treatment outcome of patients with LCH at Departement of Hematology-Oncology of Hospital Civil de Guadalajara México. Methods: It was a retrospective design and 41 pediatric patients below 18 yr were included. The diagnosis was corroborated by pathology and immunohistochemistry. Variables as age, gender, localised vs systemic disease, risk organ commitment, global survival (GS) and event free survival (EFS) were analysed. We used descriptive and inferencial statistics with SPSS program. Results: There were included 41 patients from January 1st 2012 to December 31st 2017. Relation male:female was 1.1:1. Mean presentation was localised disease (58%). Bone was the principal affected structure (34%) and it was 71% to be combined with lung, lymph node and CNS compromise. Risk organ commitment was presented in 32%, being more frecquent bone marrow and liver in 22% each one. Time induction treatment was equal or below 12 weeks in 66% of patients. The 25% of patients had reactivation of LCH, with similar lesions to the beggining in 19.5%. We found statistically significant differences between dead patients (DP) (14.6%) and not dead patients (NDP) (85.4%) in clinical presentation: localised (0% in DP vs 69% in NDP) and systemic disease (100% vs 31%) (p=0,003) and risk organ commitment (100% in DP vs 20% in NDP) (p=0,000). Median age of 13 vs 24 months was for DP and NDP respectively. Conclusion: Dead patients were younger than 13 months old, with systemic disease, and risk organ commitment. We found a later asking of medical advice in DP (6 months) vs NDP (2 months). Keys words: langerhans cell histiocytosis, multisystem disease, risk organ Figure. Figure. Disclosures No relevant conflicts of interest to declare.

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Hemophagocytic Lymphohistiocytosis (HLH) in Langerhans Cell Histiocytosis (LCH): A Multicenter Retrospective Descriptional Study

Blood ◽

10.1182/blood.v128.22.707.707 ◽

2016 ◽

Vol 128 (22) ◽

pp. 707-707 ◽

Cited By ~ 1

Author(s):

Deepak Chellapandian ◽

Rui Zhang ◽

Michael Jeng ◽

Cor Van Den Bos ◽

Vicente Santa-María López ◽

...

Keyword(s):

Diagnostic Criteria ◽

Hemophagocytic Lymphohistiocytosis ◽

Langerhans Cell Histiocytosis ◽

Conflicts Of Interest ◽

Interleukin 2 ◽

Langerhans Cell ◽

Braf V600e ◽

Bone Lesions ◽

Normal Reference ◽

Increased Risk

Abstract Introduction: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by the accumulation of CD1a+ CD207+ histiocytes. Hemophagocytic lymphohistiocytosis (HLH), a non-malignant histiocytic disorder, is typified by the accumulation and activation of CD8+ T cells and macrophages, which secrete high levels of pro-inflammatory cytokines. The co-existence of LCH and HLH has been reported, albeit rarely, and is believed to be associated with a poorer outcome. To better understand the relationship between these two conditions, in this study we sought to describe the incidence, risk factors for development, and outcome of HLH when it develops in children and young adults with multisystem-LCH (MS-LCH). Methods: We conducted a retrospective study involving 14 centers and collected data on 384 MS-LCH patients aged less than 30 years and who were diagnosed between year 2000 and 2015. Data collected on the eligible patients included clinical information at the time of LCH diagnosis, clinical and laboratory parameters at HLH diagnosis (for those who developed HLH), treatment and disease outcome. Patients who developed HLH were classified as having "true-HLH", which was defined as disease fulfilling 5 of 8 HLH-2004 diagnostic criteria or as "HLH-like" disorder, which was defined as fulfilling <5 of 8 HLH diagnostic criteria but whose disease status was suggestive of HLH and treated with HLH- and/or LCH-directed therapy. Results: Of 384 MS-LCH patients, 44 (11%) were identified with HLH (29 with true HLH and 15 with an HLH-like disorder), ranging in age from 15 days to 20.6 years (median, 1.12 years). The majority of MS-LCH patients who also had HLH were females (n=27) and had accompanying risk organ (liver, spleen and/or hematopoietic system) involvement (RO+) (n=40), as opposed to non-HLH MS-LCH patients. Among nine HLH patients tested for BRAF V600E mutation status, eight were found to be positive. Twenty (45%) patients developed HLH (true or HLH-like) concurrent (±7 days) with LCH diagnosis, while 24 (55%) developed HLH >7 days before or after LCH diagnosis. The 3-year cumulative incidence of HLH (true or HLH-like) in MS-LCH was 16.8%. The 5-year overall survival of LCH patients without HLH was 98 ± 9%, while survival for those with an HLH-like disorder or true-HLH was 75 ± 12% and 70 ± 14%, respectively (P<0.0001). Age <2 years, female gender, RO+ and lack of bone involvement at LCH diagnosis were each independently associated with increased risk for HLH. Among 20 HLH patients with available data, the median soluble interleukin-2 receptor level (sIL-2R) was 16,220 U/mL (range, 1,149 to 60,420 U/mL) (normal reference <2,400 U/mL), ferritin was 505 ng/mL (range, 28 to 26,660 ng/mL) (normal reference <500 ng/mL), and sIL-2R/ferritin ratio was 42. Conclusion: The development of HLH in patients with MS-LCH was not uncommon and associated with a poorer prognosis. Young females with RO+ MS-LCH who lack bone lesions at LCH diagnosis were at increased risk of developing HLH. Ferritin levels appear to be lower in comparison to patients who develop HLH in other contexts. There are overlapping features between MS-LCH and HLH that make the clinical distinction between these disorders difficult. Accordingly, improved biomarkers are needed to facilitate the identification of HLH in patients with MS-LCH. It is anticipated that early identification of HLH and prompt intervention may improve the outcome for affected individuals. Future prospective studies are needed to better understand the underlying mechanisms and identify more effective therapies. Disclosures No relevant conflicts of interest to declare.

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