Incidence and pattern of radiological central nervous system Langerhans cell histiocytosis in children: a population based study

Dural involvement in central nervous system langerhans cells histiocytosis (LCH) on FDG PET/CT: Case report and review of CNS manifestations of LCH on PET/CT

We report a case of multisystem Langerhans cell histiocytosis in a pediatric patient with central nervous system involvement, highlighting F-18(FDG) uptake characteristics of dural sites of disease. We also highlight the advantages of functional data offered by FDG-PET as a useful follow-up tool to assess viability and, therefore, treatment response of previously known central nervous system lesions. The utility of recognizing characteristic patterns of FDG uptake in dural disease is also applicable in cases of diagnostic uncertainty, such as when evaluating isolated dural lesions or when distinguishing between Langerhans cell histiocytosis and similar appearing lesions such as meningiomas.

[Central nervous system disorders secondary to histiocytoses: neurodegeneration with potential for improvement]

Histiocytoses, including Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD), are inflammatory myeloid tumors in which monocyte lineage cells aggregate in various organs, causing tissue damage. Most of these tumors harbor oncogenic mutations in mitogen-activated protein kinase (MAPK) pathway genes, typified by BRAFV600E. Some patients with LCH develop bilateral symmetrical cerebellar lesions and brain atrophy several years after diagnosis when the initial symptoms disappear, leading to cerebellar ataxia and higher cerebral dysfunction. A similar neurological disorder has also been reported in ECD. This neurological disorder can be improved with MAPK inhibitors. When patients with this neurological disorder are identified among neurodegeneration of unknown etiology or histiocytosis patients and treated early with MAPK inhibitors, the disorder can be reversible.

Langerhans cell histiocytosis of the thyroid mimicking thyroiditis in a boy: a case report and literature review

BACKGROUND

Langerhans cell histiocytosis affecting the thyroid commonly presents with nonspecific clinical and radiological manifestations. Thyroid Langerhans cell histiocytosis is typically characterized by non-enhancing hypodense lesions with an enlarged thyroid on computed tomography medical images. Thyroid involvement in LCH is uncommon and typically encountered in adults, as is salivary gland involvement. Therefore, we present a unique pediatric case featuring simultaneous salivary and thyroid involvement in LCH.

CASE PRESENTATION

A 3-year-old boy with complaints of an anterior neck mass persisting for 1 to 2 months, accompanied by mild pain, dysphagia, and hoarseness. A physical examination revealed a 2.5 cm firm and tender mass in the left anterior neck. Laboratory examinations revealed normal thyroid function test levels. Ultrasonography revealed multiple heterogeneous hypoechoic nodules with unclear and irregular margins in both lobes of the thyroid. Contrast-enhanced neck computed tomography revealed an enlarged thyroid gland and bilateral submandibular glands with non-enhancing hypointense nodular lesions, and multiple confluent thin-walled small (< 1.5 cm) cysts scattered bilaterally in the lungs. Subsequently, a left thyroid excisional biopsy was performed, leading to a histopathological diagnosis of LCH. Immunohistochemical analysis of the specimen demonstrated diffuse positivity for S-100, CD1a, and Langerin and focal positivity for CD68. The patient received standard therapy with vinblastine and steroid, and showed disease regression during regular follow-up of neck ultrasonography.

CONCLUSIONS

Involvement of the thyroid and submandibular gland as initial diagnosis of Langerhans cell histiocytosis is extremely rare. It is important to investigate the involvement of affected systems. A comprehensive survey and biopsy are required to establish a definitive diagnosis.

Orbital histiocytosis and fibrohistiocytosis: the clinicopathological characteristics of 117 patients, over a decade of experience

PURPOSE

To describe the clinicopathological features of a large cohort of patients with orbital histiocytoses and fibrohistiocytosis, such as Langerhans cell histiocytosis (LCH) and non-LCH disorders, and correlate patients' clinical characteristics with their pathological diagnosis.

METHODS

In this retrospective study, medical records of patients presenting to Farabi Eye Hospital, a tertiary eye care center in Tehran, Iran, from 2010 until 2022, were reviewed. Patients' demographics, chief complaint, location and laterality of the tumor, best-corrected visual acuity, presence of bone erosion on imaging, and their pathological diagnosis were retrieved. Excisional biopsy was performed and evaluated through light microscopy and immunohistochemistry study for their respective markers, including CD1a, CD68, CD207, and S100.

RESULTS

A total of 117 patients with 11 pathological subtypes of histiocytoses and fibrohistiocyosis were identified, with 56.4% male and 43.6% female patients. The mean age at presentation was 23.4 years (range 1.5 months-73 years). Swelling and palpable mass were the most common chief complaints. LCH was the most common pathology (32.5%), followed by juvenile xanthogranuloma (26.5%) and adult xanthogranuloma (21.4%). Age, lesion location, and bone erosion had a statistically significant difference among the various diagnosed subtypes.

CONCLUSIONS

Histiocytoses and fibrohistiocytosis are diverse and rare disorders potentially involving multiple organ systems. Ophthalmic manifestations of these diseases are even more uncommon. We reviewed their orbital presentation along with their respective histopathological findings. Our results also suggested that an orbital CT scan can be of diagnostic value to discriminate LCH from other histiocytic pathologies.

An adult progressive Langerhans cell histiocytosis with central nervous system involvement for 10 years: A case report

Introduction

Langerhans cell histiocytosis (LCH) is a rare disease that usually occurs in children <15 years of age. Adult-onset LCH is extremely rare. Previous published guidelines and studies mainly focused on pediatric patients. The rarity and also insufficient knowledge of LCH in adults, especially central neuvous system (CNS) involvement of LCH, often resulted in missed and delayed diagnosis.

Case presentation

A 35-year-old woman presented with cognitive impairment, anxietydepression, decreased eyesight, skin rash, hypernatremia, gonadal hormone deficiency and hypothyroidism. She had experienced menstrual disturbance and infertility since 10 years ago. MRI examination showed a mass lesion in the hypothalamic-pituitary region. Sighs of radiologic neurodegeneration were not found on brain MRI scans, however. Biopsy of skin rash confirmed the the diagnosis of multisystem LCH. BRAF V600E mutation was detected in the peripheral blood mononuclear cells. She accepted combination chemotherapy of vindesine and prednisone and accquired partial remission. The patient died of severe pneumonia during the second course of chemotherapy.

Conclusion

Given the complicated differential diagnoses of neuroendocrine disorders, it was essential to be aware of CNS involvement of LCH at first, especially in adults. BRAF V600E mutation may participated in disease progression.

Ophthalmic histiocytic lesions (diseases of the L group): A multicenter clinicopathological study of 18 cases and review of literature

INTRODUCTION

Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) are rare histiocytic disorders in the L (Langerhans) group diseases. They range from self-limited benign diseases to lethal disseminated forms.

METHODS

This retrospective study was conducted in 3 tertiary hospitals in Saudi Arabia and Brazil. Histopathological records were searched for all patients diagnosed with ocular and periocular histiocytic disorders from January 1993 to December 2018. Histopathological slides and medical files were reviewed for data collection and simple analysis of demographics, clinical manifestations, and management. The relevant literature is reviewed.

RESULTS

Twenty-two eyes of 18 patients with biopsy-proven histiocytic disorders in the L group were included. Female-to-male ratio was 1.25:1. Average age at presentation was 14 years (range, 1-54). LCH was diagnosed in 14 eyes, while eight eyes had ECD. All LCH cases were unilateral and confined to the bone as cases of eosinophilic granuloma (EG), while patients with ECD were bilateral. Commonest presentations in EG and ECD were eyelid swelling (85.7%) and periocular xanthomas (75%), respectively. Orbit was involved in 100% of EG cases, with bony erosion in 54.5%. Relevant systemic involvement was found in 100% of ECD and 21% of EG cases. Surgical intervention was needed in 16 of the 22 eyes (72.7%). All EG and 25% of patients with ECD required surgical excision.

CONCLUSIONS

Histiocytic disorders are a rare group of diseases, including the L group. Relevant systemic associations require specific and selective therapy. A high clinical index and multidisciplinary collaboration are essential for the proper evaluation and management of these patients.

Langerhans cell histiocytosis involving only the thymus in an adult: A case report

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare disease of unknown etiology. LCH involving the thymus is mainly seen in pediatric patients and is extremely rare in adults. In this report, we describe a rare case of LCH originating from the thymus in an adult.

CASE SUMMARY

A 56-year-old man was admitted in April 2022 with complaints of intermittent dizziness since 2020, which had worsened in the previous 10 d. The physical chest examination was negative, and there was a history of hypertension for > 2 years. Chest computed tomography showed a nodular soft tissue density shadow in the anterior mediastinum measuring approximately 13 mm × 9 mm × 8 mm. Postoperative pathological findings confirmed the diagnosis of LCH.

CONCLUSION

It is challenging to differentiate LCH involving the thymus from thymoma in imaging features. Pathological biopsy remains the gold standard when an anterior mediastinal occupying lesion is found.

Socio-behavioral dysfunction in disorders of hypothalamic-pituitary involvement: The potential role of disease-induced oxytocin and vasopressin signaling deficits

Disorders involving hypothalamic and pituitary (HPIT) structures-including craniopharyngioma, Langerhans cell histiocytosis, and intracranial germ cell tumors-can disrupt brain and endocrine function. An area of emerging clinical concern in patients with these disorders is the co-occurring socio-behavioral dysfunction that persists after standard hormone replacement therapy. Although the two neuropeptides most implicated in mammalian social functioning (oxytocin and arginine vasopressin) are of hypothalamic origin, little is known about how disease-induced damage to HPIT structures may disrupt neuropeptide signaling and, in turn, impact patients' socio-behavioral functioning. Here we provide a clinical primer on disorders of HPIT involvement and a review of neuropeptide signaling and socio-behavioral functioning in relevant animal models and patient populations. This collective evidence suggests that neuropeptide signaling disruptions contribute to socio-behavioral deficits experienced by patients with disorders of HPIT involvement. A better understanding of the biological underpinnings of patients' socio-behavioral symptoms is now needed to enable the development of the first targeted pharmacological strategies by which to manage patients' socio-behavioral dysfunction.

Integrated imaging of systemic Langerhans cell histiocytosis in an infant

Langerhans cell histiocytosis (LCH) is a myeloid neoplasm characterized by a clonal proliferation of CD1a+/CD207+ dendritic cells. Although individuals of any age can be affected, the disease is most common in infants younger than 5 years of age, especially males. A wide range of manifestations, from asymptomatic to aggressive, have been described, along with multiorgan involvement. Even though the majority of bone lesions are observed, skin, lymph nodes, brain and lungs can also be involved. The involvement of hematopoietic system, including bone marrow, liver and spleen, is less frequent yet associated with worse prognosis, due to a worse treatment response. Diagnosis of LCH is based on the integration of clinical, laboratory, and radiological data; however, only histopathological examination might confirm it. As far as the spleen involvement is concerned, according to literature, it has been reported in about 15% patients with multisystem involvement, nonetheless only a few cases show parenchymal lesions. The present study reports the case of an infant with LCH with multisystem involvement, including bone, skin, liver, and spleen, with evidence of parenchymal lesions.

Screening for neurodegeneration in Langerhans cell histiocytosis with neurofilament light in plasma

Patients with Langerhans cell histiocytosis (LCH) may develop progressive neurodegeneration in the central nervous system (ND‐CNS‐LCH). Neurofilament light protein (NFL) in cerebrospinal fluid (CSF) is a promising biomarker to detect and monitor ND‐CNS‐LCH. We compared paired samples of NFL in plasma (p‐NFL) and CSF in 10 patients (19 samples). Nine samples had abnormal CSF‐NFL (defined as ≥380 ng/l) with corresponding p‐NFL ≥ 2 ng/l. Ten samples had CSF‐NFL < 380 ng/l; eight (80%) with p‐NFL < 2 ng/l (p < 0.001; Fisher's exact test). Thus, our results suggest that p‐NFL may be used to screen for ND‐CNS‐LCH. Further studies are encouraged, including the role of p‐NFL for monitoring of ND‐CNS‐LCH.

Ophthalmic histiocytic lesions: a baseline demographic and clinicopathological study of 28 cases from two eye centers

PURPOSE

Ophthalmic histiocytic lesions comprise a heterogeneous rare group of disorders that are characterized by an abnormal proliferation of histiocytes and may affect all age groups of both sexes. The aim of this study was to highlight the basic demographic, clinical, and histopathological characteristics of this rare group of diseases in ophthalmic practice, which has not been previously studied in this area. Only individual cases have been previously reported.

METHODS

This was a retrospective study of all biopsied ocular and periocular histiocytic lesions from two centers, King Khaled Eye Specialist Hospital (KKESH) and King Abdulaziz University Hospital (KAUH) in Riyadh, Saudi Arabia, from January 1993 to December 2018. The histopathological diagnosis was confirmed, and the cases were re-classified by reviewing all histopathological slides. The corresponding demographic and clinical data were analyzed. A relevant literature review was also carried out for comparison of our collected analyzed data to published data and to draw our own conclusions.

RESULTS

A total of 34 ocular/periocular histiocytic lesions in 28 patients who were mostly Saudis (92.9%) were included. The male-to-female ratio was 4:3. The median age at presentation was 6.4 years (range: 2.8-35 years). Twenty-two patients had unilateral involvement, and six patients had bilateral lesions. In patients with Langerhans cell histiocytosis (LCH; L group), the most common presenting findings were eyelid swelling (75%), periocular tenderness (37.5%), proptosis/globe displacement (37.5%) eyelid erythema (25%), and orbital pain (12.5%). In patients with Rosai Dorfman disease (RDD; R group), proptosis/globe displacement occurred in all patients and 80% had decreased vision. Patients in the C group (Cutaneous non-LCH histiocytoses) had variable clinical features because of the different locations of the histiocytic lesions, with the majority involving the eyelids (66.7%). Diagnosis was accurately reached clinically in 38.8%, 33.7%, and 46.7% of patients in the L, C, and R groups, respectively. Overall, the clinical diagnosis was in concordance with the histopathologic diagnosis in 14 out of 34 lesions (41.2%).

CONCLUSIONS

Histiocytic disease is more likely to be overlooked clinically owing to its rarity. In the C group, juvenile xanthogranuloma (JXG) was the most commonly encountered histiocytic lesion and had a tendency to present at a later age with extremely rare intraocular involvement in contrast to previously published reports. The median age at presentation was higher in group R. All patients in group L had strictly unilateral disease, while RDD (group R) was most commonly bilateral. Future research on genetic aspects, management, and prognosis is necessary.

Ocular Involvement in the Histiocytoses: A Literature Review with an Illustrative Case Series

Purpose: To describe and illustrate recent reclassification and clinical descriptions of the histiocytoses, diagnosis and management, and effects on the eye and adnexaePatients and methods: Literature review with an illustrative case series of seven patients with histiocytosis and ophthalmic involvement from a single tertiary centre.Results: Skin lesions with signs including eyelid mass, orbital bone destruction, bizarre keratic precipitates, limbal or iris mass, haemorrhagic anterior uveitis, subretinal lesions of uncertain etiology, ischaemic retinopathy, optic neuropathy, and apparent steroid-resistant inflammations should be comprehensively investigated.Conclusions: Ophthalmic involvement in histiocytosis is rare. Clinical manifestations vary from limited single-organ disease to lethal systemic infiltration or malignancy. Radiology may identify lesions for biopsy. Histology with appropriate markers is essential. Oncology advice may be required.

Long-term outcome, clinical course and treatment approaches of paediatric langerhans cell histiocytosis: A greek reference centre report

AIM

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia with diverse clinical behaviour. In this article, we studied the clinical course, management and long-term outcomes of a paediatric cohort treated by our reference centre.

METHODS

We retrospectively studied 66 children with LCH, consecutively diagnosed by a Greek reference centre from 1974 to 2020.

RESULTS

The patients had a median age of 3.9 (range 0.0-15.9) years, 39 and 6 patients were diagnosed with unifocal or multifocal single system disease and 14 and 7 had multisystem disease with or without risk organ involvement. No late occurrence of clinical neurodegenerative disease or diabetes insipidus were observed at a median follow-up period of 4.1 (range 0.5-27.7) years. The 10-year event-free survival and overall survival were 65.0% and 90.3% and improved significantly over a 45-year period. Survival was superior in single system than multisystem cases. BRAF V600E mutation was found in 8/14 tested patients. Reactivation occurred in 12/66 patients (18.2%); 11 achieved remission and one patient died after a second relapse.

CONCLUSION

LCH survival rates significantly increased in our cohort over time. Reactivation occurred in 18.2% patients, but no late neurodegeneration was found. The prognostic value of single system disease status vs. multisystem LCH was confirmed.

Neuroendocrine manifestations of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare inflammatory myeloid neoplasia that can affect any organ or system in the human body. It is usually diagnosed during childhood but can also affect adults. Recent studies have demonstrated involvement of the hypothalamo-pituitary axis (HPA) in a significant proportion of patients with deficiencies in both anterior and posterior pituitary function that in the majority of cases are permanent and require specific hormone replacement regimes. Central diabetes insipidus is considered the most frequent abnormality of HPA involvement in LCH and can be encountered either as isolated deficiency or along with other pituitary deficiencies. Complete hormonal evaluation of pituitary hormones and long-term follow-up of LCH patients are strongly recommended, especially when pituitary involvement is established.

Central diabetes insipidus in children: Diagnosis and management

Central diabetes insipidus (CDI) is a complex disorder in which large volumes of dilute urine are excreted due to arginine-vasopressin deficiency, and it is caused by a variety of conditions (genetic, congenital, inflammatory, neoplastic, traumatic) that arise mainly from the hypothalamus. The differential diagnosis between diseases presenting with polyuria and polydipsia is challenging and requires a detailed medical history, physical examination, biochemical approach, imaging studies and, in some cases, histological confirmation. Magnetic resonance imaging is the gold standard method for evaluating the sellar-suprasellar region in CDI. Pituitary stalk size at presentation is variable and can change over time, depending on the underlying condition, and other brain areas or other organs - in specific diseases - may become involved during follow up. An early diagnosis and treatment are preferable in order to avoid central nervous system damage and the risk of dissemination of germ cell tumor, or progression of Langerhans Cell Histiocytosis, and in order to start treatment of additional pituitary defects without further delay. This review focuses on current diagnostic work-up and on the role of neuroimaging in the differential diagnosis of CDI in children and adolescents. It provides an update on the best approach for diagnosis - including novel biochemical markers such as copeptin - treatment and follow up of children and adolescents with CDI; it also describes the best approach to challenging situations such as post-surgical patients, adipsic patients, patients undergoing chemotherapy and/or in critical care.

Clinical outcomes of childhood Langerhans cell histiocytosis in Taiwan: A single-center, 20-year experience

BACKGROUND/PURPOSE

The Taiwan Pediatric Oncology Group (TPOG) initiated two consecutive protocols for treating pediatric patients with Langerhans cell histiocytosis (LCH) since 1994. However, the results have not been analyzed and reported. This study aimed to investigate the survival outcomes of childhood LCH at the National Taiwan University Hospital over the past 20 years.

METHODS

Treatment of pediatric patients with LCH according to TPOG protocols at the National Taiwan University Hospital began in 1994. During 1994-2003, patients were treated using the TPOG LCH-94 protocol. After 2003, patients were treated using the TPOG LCH-2003 protocol. Clinical data of these patients were obtained retrospectively by reviewing electronic medical records. Patients were followed up until July 31, 2018.

RESULTS

Fifty-three newly diagnosed pediatric patients with LCH were treated at National Taiwan University Hospital during 1994-2015. Twenty-nine (54.7%) were treated with the TPOG LCH-94 protocol, and 24 (45.3%) were treated with the TPOG LCH-2003 protocol. The 5-year event-free survival and overall survival rates were 96.2 ± 2.6% standard error (SE) and 98.1 ± 1.9% (SE), respectively. Overall survival and 5-year event-free survival between patients treated with the TPOG LCH-94 and TPOG LCH-2003 protocols showed no significant difference. Multisystem, liver, or spleen diseases were associated with significantly bad survival outcomes. Among at-risk-organ involvement in LCH, liver involvement was an independent factor for poor prognosis.

CONCLUSION

Clinical outcomes of children with LCH in Taiwan was good. The results of this study may help in the better classification of risk grouping for protocol designs in the future.

Update on the classification of T-cell lymphomas, Hodgkin lymphomas, and histiocytic/dendritic cell neoplasms

Introduction: The classification of lymphomas is based on the postulated normal counterparts of lymphoid neoplasms and currently constitutes over 100 definite or provisional entities. As this number of entities implies, lymphomas show marked pathological, genetic, and clinical heterogeneity. Recent molecular findings have significantly advanced our understanding of lymphomas. Areas covered: The World Health Organization (WHO) classification of lymphoid neoplasms was updated in 2017. The present review summarizes the new findings that have been gained in the areas of mature T-cell neoplasms, Hodgkin lymphomas, and histiocytic/dendritic cell neoplasms since the publication of the 2017 WHO classification. Expert opinion: Although formal revisions to the WHO classification are published only periodically, our understanding of the pathologic, genetic, and clinical features of lymphoid neoplasms is constantly evolving, particularly in the age of -omics technologies and targeted therapeutics. Even in the relatively short time since the publication of the 2017 WHO classification, many significant findings have been identified in the entities covered in this review.

Neuroimaging in Hereditary Spastic Paraplegias: Current Use and Future Perspectives

Hereditary spastic paraplegias (HSP) are a large group of genetic diseases characterized by progressive degeneration of the long tracts of the spinal cord, namely the corticospinal tracts and dorsal columns. Genotypic and phenotypic heterogeneity is a hallmark of this group of diseases, which makes proper diagnosis and management often challenging. In this scenario, magnetic resonance imaging (MRI) emerges as a valuable tool to assist in the exclusion of mimicking disorders and in the detailed phenotypic characterization. Some neuroradiological signs have been reported in specific subtypes of HSP and are therefore helpful to guide genetic testing/interpretation. In addition, advanced MRI techniques enable detection of subtle structural abnormalities not visible on routine scans in the spinal cord and brain of subjects with HSP. In particular, quantitative spinal cord morphometry and diffusion tensor imaging look promising tools to uncover the pathophysiology and to track progression of these diseases. In the current review article, we discuss the current use and future perspectives of MRI in the context of HSP.

Dramatic efficacy of dabrafenib in Erdheim-Chester disease (ECD): a pediatric patient with multiple large intracranial ECD lesions hidden by refractory Langerhans cell histiocytosis

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell form of histiocytosis that can affect the central nervous system. ECD predominantly affects adults, and only a few pediatric cases have been reported. The co-occurrence of ECD and Langerhans cell histiocytosis (LCH) is exceedingly rare. An 11-year-old boy, who was diagnosed with LCH 7 years previously, presented with multiple giant intracranial lesions. At the time of his initial diagnosis, only one intracranial lesion was observed, and it began to enlarge. Currently, up to 7 intracranial lesions can be observed in this patient. However, the diagnosis of ECD was not confirmed until this most recent open resection. The BRAF V600E mutation was detected in both LCH and ECD lesions. Dabrafenib therapy exhibited dramatic efficacy in this pediatric patient. This case represents the first successful application of dabrafenib in a pediatric patient with intracranial ECD lesions as well as mixed ECD and LCH. In this article, the authors describe the intricate diagnosis and treatment processes in this patient. Recent studies regarding treatment with BRAF inhibitors for neurological involvement in mixed ECD and LCH are also reviewed.

CNS Langerhans cell histiocytosis: Common hematopoietic origin for LCH-associated neurodegeneration and mass lesions

BACKGROUND

Central nervous system Langerhans cell histiocytosis (CNS-LCH) brain involvement may include mass lesions and/or a neurodegenerative disease (LCH-ND) of unknown etiology. The goal of this study was to define the mechanisms of pathogenesis that drive CNS-LCH.

METHODS

Cerebrospinal fluid (CSF) biomarkers including CSF proteins and extracellular BRAFV600E DNA were analyzed in CSF from patients with CNS-LCH lesions compared with patients with brain tumors and other neurodegenerative conditions. Additionally, the presence of BRAFV600E was tested in peripheral mononuclear blood cells (PBMCs) as well as brain biopsies from LCH-ND patients, and the response to BRAF-V600E inhibitor was evaluated in 4 patients with progressive disease.

RESULTS

Osteopontin was the only consistently elevated CSF protein in patients with CNS-LCH compared with patients with other brain pathologies. BRAFV600E DNA was detected in CSF of only 2/20 (10%) cases, both with LCH-ND and active lesions outside the CNS. However, BRAFV600E+ PBMCs were detected with significantly higher frequency at all stages of therapy in LCH patients who developed LCH-ND. Brain biopsies of patients with LCH-ND demonstrated diffuse perivascular infiltration by BRAFV600E+ cells with monocyte phenotype (CD14+ CD33+ CD163+ P2RY12- ) and associated osteopontin expression. Three of 4 patients with LCH-ND treated with BRAF-V600E inhibitor experienced significant clinical and radiologic improvement.

CONCLUSION

In LCH-ND patients, BRAFV600E+ cells in PBMCs and infiltrating myeloid/monocytic cells in the brain is consistent with LCH-ND as an active demyelinating process arising from a mutated hematopoietic precursor from which LCH lesion CD207+ cells are also derived. Therapy directed against myeloid precursors with activated MAPK signaling may be effective for LCH-ND. Cancer 2018;124:2607-20. © 2018 American Cancer Society.

Langerhans cell histiocytosis in children - a disease with many faces. Recent advances in pathogenesis, diagnostic examinations and treatment

Langerhans cell histiocytosis is a rare clonal disease characterized by the proliferation of CD1a-positive immature dendritic cells. The purpose of this article was to present an updated review of recent advances in the pathogenesis, clinical features, imaging and treatment of this disease. The discovery of oncogenic BRAF mutations and the presence of proinflammatory cytokines and chemokines confirmed the unusual characteristics of this disease. Currently, children with organ involvement who do not have a good response to chemotherapy and have neurodegeneration or diabetes insipidus are the most problematic patients. Further research is needed to improve the results of treatment.

Neuroradiologic manifestations of Erdheim-Chester disease

Background

We describe the neuroradiologic features of a cohort of patients with Erdheim-Chester disease.

Methods

We assessed patients at Mayo Clinic Rochester between January 1, 1990, and July 31, 2016, with pathologically confirmed Erdheim-Chester disease (n = 53).

Results

Neuroimaging, including head CT (n = 17), brain MRI (n = 39), orbital MRI (n = 15), and spine MRI (n = 16), was available for 42 participants. Median age at diagnosis was 55 years (interquartile range 46-66) with higher male prevalence (33:20). Neurologic symptoms were identified in 47% (25/53); BRAF^V600E mutation in 58% (15/26). Median follow-up was 2 years (range 0-20) with 18 patients deceased. Radiologic disease evidence was seen in dura (6/41), brainstem (9/39), cerebellum (8/39), spinal cord (2/16), spinal epidura (2/16), hypothalamic-pituitary axis (17/39), and orbits (13/42). T2 white matter abnormalities (Fazekas score ≥1) were present in 21/34 patients. Diabetes insipidus was present in 30% (16/53); 8 had abnormal hypothalamic-pituitary axis imaging. Radiographic evidence of CNS involvement (i.e., dural, brain, including Fazekas score >1, or spinal cord) occurred in 55% (22/40) and was unassociated with significantly increased mortality.

Conclusions

Erdheim-Chester disease commonly and variably involves the neuraxis. Patients with suspected Erdheim-Chester disease should undergo MRI brain and spine and screening investigations (serum sodium, serum and urine osmolality) for diabetes insipidus to clarify extent of neurologic disease.

Histiocytic lesions of the orbit: A study of 9 cases

PURPOSE

To describe the clinical presentation, treatment, and outcome of patients with histiocytic lesions of the orbit.

METHODS

Retrospective study of 9 patients treated and followed up between October 2001 and January 2018.

RESULTS

Eight patients in our series were males and one patient was female. The mean age at presentation was 16.8 years (range, 1 to 42 years). All patients had unilateral disease. The most common presenting complaint was upper eyelid swelling in 8 of 9. All patients underwent preoperative computed tomography (CT) and magnetic resonance imaging (MRI). Eight of 9 patients demonstrated orbital bone erosion with adjacent soft tissue mass. Destruction of the orbital roof and contrast enhancement of dura were detected in 3 cases. All cases underwent orbitotomy and subtotal tumor excision with additional bone curettage (4 cases) and intraorbital steroid (40 mg triamcinolone acetonide) injection (3 cases). Adjuvant systemic chemotherapy consisting of vinblastine and prednisone was administered in 3 cases with dural involvement. External radiotherapy (1000 cGy) was applied in one case because of widespread disease. Histopathologic diagnoses were eosinophilic granuloma (7 cases), necrotic xanthogranuloma (1 case), and Langerhans cell sarcoma (1 case). The mean follow-up period after diagnosis was 19.7 months (range, 1-96 months). There was no systemic or multifocal bone involvement in eosinophilic granuloma cases at initial presentation and follow-up. None of these patients developed diabetes insipidus or neurologic symptoms. The patient with Langerhans cell sarcoma died from systemic disease 1 month after diagnosis of the orbital tumor. The patient with necrotic xanthogranuloma did not develop any malignancy at 9 months follow-up.

CONCLUSIONS

Eosinophilic granuloma was the most frequently encountered orbital histiocytic lesion in our series. Eosiophilic granuloma usually responded well to subtotal tumor excision, bone curettage, and intraorbital corticosteroid injections. Systemic chemotherapy was used in cases with full thickness bone destruction and adjacent dural enhancement in an effort to prevent the development of central nervous system disease.

Evaluation and treatment of Langerhans cell histiocytosis patients with central nervous system abnormalities: Current views and new vistas

Central nervous system (CNS) involvement in Langerhans cell histiocytosis (LCH) can include mass lesions of the hypothalamic pituitary axis, choroid plexus, cerebrum, and cerebellum or magnetic resonance imaging (MRI) signal abnormalities of the cerebellum, pons, and basal ganglia. The term neurodegenerative (ND) CNS-LCH has been given to the MRI signal abnormalities and neurologic dysfunction, although initially patients may have no clinical symptoms. Standardized evaluations to better understand the natural history and response to therapy are needed. We propose guidelines for clinical, radiologic, and physiologic tests as a framework for developing the best methods of evaluation, which can then be tested in prospective treatment protocols.

Late outcomes in children with Langerhans cell histiocytosis

INTRODUCTION

Langerhans cell histiocytosis (LCH) is a rare disease with diverse clinical courses. Despite improvement in survival outcomes in the recent decades, sequelae of the disease remain a concern. This study aimed to provide information on the long-term outcomes in patients with LCH, particularly on the sequelae and any associated factors.

METHOD

Medical records of patients with diagnosis of LCH and being managed in our centre were retrospectively reviewed. Data on the courses of illness, mortality, intervention, types and time of late events were collected and analysed.

RESULTS

70 patients were included with a mean observation time of 12 years (median 10.7 years, range 1-31.3 years). Sequelae related to LCH were present in 56% (n=39), being more common in multisystem diseases and patients with reactivations. Prevalence of sequelae is as follows: orthopaedic related 27%, diabetes insipidus 19%, growth retardation 13%, cosmetic 10%, neurological 7%, hearing 7%, anterior pituitary hormone deficiency 7%, hepatobiliary 4% and ophthalmological 3%. Neurological sequelae could manifest even 10 years after initial diagnosis of LCH. Reactivations, presence of central nervous system (CNS) risk lesions and treatment with radiotherapy were associated with a higher rate of sequelae. The cumulative incidence of reactivation was 34%. Most reactivations occurred in the first 2.5 years after diagnosis.

CONCLUSION

Sequelae were common after LCH, although some were mild. Neurological sequelae could be particularly severe and debilitating. Vigilant long-term follow-up would be essential for optimising patient outcomes. Further studies on the prevention and treatment of CNS disease of LCH are warranted.

A somatic mutation in erythro-myeloid progenitors causes neurodegenerative disease

The pathophysiology of neurodegenerative diseases is poorly understood, and therapeutic options are few. Neurodegenerative diseases are hallmarked by progressive neuronal dysfunction and loss, associated with chronic glial activation¹. Whether microglial activation, which is viewed in general as a secondary process, is detrimental or protective in neurodegeneration remains unclear^1–8. Late-onset neurodegenerative disease observed in patients with histiocytoses^9–12, which are clonal myeloid diseases associated with somatic mutations in the RAS/MEK/ERK pathway such as BRAF^{V600E 13–17}, suggests a possible role of somatic mutations in myeloid cells in neurodegeneration. Yet expression of BRAF^V600E in the hematopoietic stem cell (HSC) lineage causes leukemic and tumoral diseases but not neurodegenerative disease^18,19. Microglia belong to a lineage of adult tissue-resident myeloid cells that develop during organogenesis from yolk sac erythro-myeloid progenitors (EMP) distinct from HSC^20–23. We thus hypothesized that a somatic BRAF^V600E mutation in the EMP lineage may cause neurodegeneration. Here we show that mosaic expression of BRAF^V600E in EMP results in clonal expansion of tissue-resident macrophages and a severe late-onset neurodegenerative disorder, associated with accumulation of ERK-activated amoeboid microglia in mice, also observed in human histiocytoses patients. In the murine model, neurobehavioral signs, astrogliosis, amyloid precursor protein deposition, synaptic loss and neuronal death were driven by ERK-activated microglia and were preventable by BRAF inhibition. These results identify the fetal precursors of tissue-resident macrophages as a potential cell-of-origin for histiocytoses, and demonstrate in mice that a somatic mutation in the EMP lineage can drive late-onset neurodegeneration. Moreover, these data identify activation of the MAP kinase pathway in microglia as a cause of neurodegeneration, and provide opportunities for therapeutic intervention aimed at preventing neuronal death in neurodegenerative diseases.

Histiocytoses: emerging neoplasia behind inflammation

Histiocytoses are disorders characterised by inflammation and the accumulation of cells derived from the monocyte and macrophage lineages, which results in tissue damage. Although they are often considered rare disorders with protean clinical manifestations, considerable advances in the understanding of their genetics have led to increased clinical recognition of these conditions, and fuelled further insights into their pathogenesis. In this Review, we describe insights into the cells of origin, molecular pathology, clinical features, and treatment strategies for some of the most common histiocytic disorders, including Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease. With the discovery of recurrent mutations affecting the mitogen-activated protein kinase and mTOR-AKT pathways in some of these histiocytoses, our understanding of these diseases has now evolved from the concept of a primary inflammatory condition to that of a clonal neoplastic disease. This understanding has led to the development of effective mechanism-based therapeutic strategies for patients with histiocytic diseases.

Evaluation of pituitary uptake incidentally identified on 18F-FDG PET/CT scan

The clinical significance of pituitary uptake on routine whole body ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computer tomography (PET/CT) is not completely characterized. We seek to assess the potential differential diagnosis/underlying etiology of pituitary FDG uptake incidentally identified on routine PET/CT scans. A total of 24,007 PET/CT whole body scans in recent 5 years were retrospectively reviewed. Patients with maximum standardized uptake value (SUVmax) > 4.1 in the pituitary glands were identified. Cases with a known history of pituitary disorders were excluded. Nineteen cases were identified with incidental pituitary FDG uptake which all had a final pathological diagnosis/clinical follow up. Among them, there were 9 primary pituitary tumors, with SUVmax ranging from 4.7 to 29.3 (13.6 ± 9.8); 3 metastatic malignancy with SUVmax ranging from 7.3 to 32.3 (16.0 ± 10.6); 3 Langerhans cell histiocytosis (LCH) with SUVmax ranging from 6.0 to 26.0 (15.0 ± 10.2); 1 pituitary lymphocytic hypophysitis with SUVmax of 4.7. Of note, 3 cases with SUVmax of 7.5,7.9 and 9.6 showed no relevant clinical symptoms with negative results on subsequent magnetic resonance (MR) and were counted as benign physiologic uptake. The most common differential diagnosis of incidental pituitary uptake on routine whole body PET/CT scans was primary pituitary tumors, followed by metastatic malignancy, Langerhans cell histiocytosis, and inflammatory lymphocytic hypophysitis. Of note, benign physiologic uptake without corresponding lesions could also occur in our population.

Lymphoma classification update: T-cell lymphomas, Hodgkin lymphomas, and histiocytic/dendritic cell neoplasms

INTRODUCTION

Lymphomas are classified based on the normal counterpart, or cell of origin, from which they arise. Because lymphocytes have physiologic immune functions that vary both by lineage and by stage of differentiation, the classification of lymphomas arising from these normal lymphoid populations is complex. Recent genomic data have contributed additional depth to this complexity. Areas covered: Lymphoma classification follows the World Health Organization (WHO) system, which reflects international consensus and is based on pathological, genetic, and clinical factors. The present review focuses on the classification of T-cell lymphomas, Hodgkin lymphomas, and histiocytic and dendritic cell neoplasms, summarizing changes reflected in the 2016 revision to the WHO classification. These changes are critical to hematologists and other clinicians who care for patients with these disorders. Expert commentary: Lymphoma classification is a continually evolving field that needs to be responsive to new clinical, pathological, and molecular understanding of lymphoid neoplasia. Among the entities covered in this review, the 2016 revisions in the WHO classification particularly impact T-cell lymphomas, including a new umbrella category of T-follicular helper cell-derived lymphomas and evolving recognition of indolent T-cell lymphomas and lymphoproliferative disorders.

Pediatric Suprasellar Tumors

The various childhood suprasellar tumors, while pathologically distinct, present similar clinical and surgical challenges as a result of their common anatomic location. These lesions are in close proximity to or may invade the optic nerve and chiasm, pituitary gland and infundibulum, hypothalamus, and third ventricle, leading to presenting features including visual field loss, impairment in visual acuity, endocrine dysfunction, and hydrocephalus. Though many suprasellar lesions are relatively benign in pathology, treatment may be complicated by high surgical morbidity resulting from damage to the hypothalamic-pituitary axis. Here we review the most frequent pediatric lesions occurring in the suprasellar region: craniopharyngioma, chiasmatic glioma, germ cell tumor, Rathke cleft and arachnoid cysts, pituitary adenoma, and histiocytosis. This review outlines both common presenting features and differentiating aspects of these lesions. It also includes classic radiographic presentations and treatment considerations for each lesion.

Diffuse Encephalopathy Associated with Isolated Cerebral Langerhans Cell Histiocytosis

BACKGROUND

Langerhans cell histiocytosis is a rare disease of the monocyte-macrophage system. Abnormalities of the hypothalamic-pituitary region are common in individuals with central nervous system involvement.

PATIENT DESCRIPTION

This six-year-old boy developed rapidly progressive aggressive behavior, central diabetes insipidus, and repeated complex partial seizures. Magnetic resonance imaging revealed a diffuse leukoencephalopathy-like pattern and numerous infratentorial and supratentorial granulomatous nodules in the brain parenchyma along with infundibular and hypothalamic mass lesions. Stereotactic serial biopsies enabled histopathologic and immunohistochemical diagnosis of Langerhans cell histiocytosis.

CONCLUSIONS

Similar MRI findings have rarely been described in the literature. These findings represent part of the broad neuroradiological spectrum of Langerhans cell histiocytosis of the nervous system in children.

Langerhans Cell Histiocytosis of the Orbit: Spectrum of Disease and Risk of Central Nervous System Sequelae in Unifocal Cases

PURPOSE

To describe the spectrum of disease extent and clinical response in Langerhans cell histiocytosis (LCH) presenting with orbital involvement and to determine if unifocal orbital disease increases the risk for central nervous system sequelae (CNS-LCH).

METHODS

Retrospective chart review of patients with orbital LCH representing a range of severity treated at the Children's Hospital of Wisconsin from 2003 to 2011; analysis of current international treatment protocols; literature review.

RESULTS

Six patients presenting with orbital LCH are described: 1 with unifocal orbital disease completely responsive to local measures; 1 with multifocal bone disease completely responsive to local intervention; 1 with unifocal orbital disease incompletely responsive to surgical intervention, and requiring systemic chemotherapy; and 3 with multisystem disease at presentation. Literature review identified 806 cases of CNS-LCH. Orbital involvement could be determined in 11 cases. Of these, 6 had multisystem disease and 3 had multifocal bone disease; 1 presented with unifocal orbital disease but progressed to multifocal bone involvement; 1 had insufficient clinical information to distinguish unifocal from multisite presentation. No cases of CNS-LCH directly resulted from isolated unifocal orbital disease.

CONCLUSIONS

Initial treatment of orbital LCH should depend on disease extent at diagnosis. Unifocal cases that completely respond to biopsy, curettage, and/or corticosteroid instillation may be managed with initial oncologic staging and careful long-term observation, with default to chemotherapy for local recurrence or multisite progression. There is currently little evidence that unifocal orbital disease increases the risk for CNS-LCH and therefore warrants prophylactic systemic chemotherapy in all patients.

Coexistence of intracranial Langerhans cell histiocytosis and Erdheim-Chester disease in a pediatric patient: a case report

INTRODUCTION

The co-occurrence of Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) is extremely rare and almost all cases were reported in adults.

CASE REPORT

We describe a case of intracranial LCH and ECD that was confirmed by histopathological and molecular studies. A three-year-old boy presented with headache and right exophthalmos and brain magnetic resonance images (MRI) revealed multiple intracranial tumors. Whole body MRI showed osteolytic lesions typical of LCH in flat bones and osteosclerotic changes typical of ECD in long bones.

DISCUSSION

Histologically, the biopsy samples from the posterior fossa and occipital skull mass revealed areas of both LCH and ECD. Immunohistochemically, the LCH contained CD1a-positive Langerhans cells and the ECD had CD1a-negative, CD68-positive foamy histiocytes. BRAF (V600E) mutations were detected in both the LCH and ECD areas. The coexistence of LCH and ECD in the same biopsy and the BRAF (V600E) mutation status in both histologic types support the recent re-classification of the histiocytic disorder into LCH, ECD, and "mixed histiocytosis", which reflects tumorigenesis for all three from a common progenitor cell.

Social/economic costs and health-related quality of life in patients with histiocytosis in Europe

OBJECTIVE

The aim of this study was to determine the economic burden from a societal perspective and the health-related quality of life (HRQOL) of patients with histiocytosis in Europe.

METHODS

We conducted a cross-sectional study of patients with histiocytosis from France, Germany, Italy, Spain, Bulgaria, the UK, and Sweden. Data on demographic characteristics, health resource utilisation, informal care, loss of labour productivity and HRQOL were collected from the questionnaires completed by patients or their caregivers. HRQOL was measured with the EuroQol 5-domain (EQ-5D) questionnaire.

RESULTS

A total of 134 patients (35 France, 32 Germany, 30 Italy, 24 Spain, 7 Bulgaria, 4 UK and 2 Sweden) completed the questionnaire. The average annual costs ranged from € 6832 to € 33,283 between countries, the year of reference being 2012. Estimated direct healthcare costs ranged from € 1698 to € 18,213; direct nonhealthcare costs ranged from € 2936 to € 17,622 and labour productivity losses ranged from € 1 to € 8855. The mean EQ-5D score for adult histiocytosis patients was estimated at between 0.32 and 0.85, and the mean EQ-5D visual analogue scale score was estimated at between 50.00 and 66.50.

CONCLUSION

The main strengths of this study lie in our bottom-up approach to costing and in the evaluation of histiocytosis patients from a broad perspective (societal costs). This type of analysis is very scarce in international literature for rare diseases in comparison with other illnesses. We conclude that histiocytosis patients incur considerable societal costs and experience substantial deterioration in HRQOL.

Revised classification of histiocytoses and neoplasms of the macrophage-dendritic cell lineages

The histiocytoses are rare disorders characterized by the accumulation of macrophage, dendritic cell, or monocyte-derived cells in various tissues and organs of children and adults. More than 100 different subtypes have been described, with a wide range of clinical manifestations, presentations, and histologies. Since the first classification in 1987, a number of new findings regarding the cellular origins, molecular pathology, and clinical features of histiocytic disorders have been identified. We propose herein a revision of the classification of histiocytoses based on histology, phenotype, molecular alterations, and clinical and imaging characteristics. This revised classification system consists of 5 groups of diseases: (1) Langerhans-related, (2) cutaneous and mucocutaneous, and (3) malignant histiocytoses as well as (4) Rosai-Dorfman disease and (5) hemophagocytic lymphohistiocytosis and macrophage activation syndrome. Herein, we provide guidelines and recommendations for diagnoses of these disorders.

Early Diagnosis and Monitoring of Neurodegenerative Langerhans Cell Histiocytosis

Background

Neurodegenerative Langerhans Cell Histiocytosis (ND-LCH) is a rare, unpredictable consequence that may devastate the quality of life of patients cured from LCH. We prospectively applied a multidisciplinary diagnostic work-up to early identify and follow-up patients with ND-LCH, with the ultimate goal of better determining the appropriate time for starting therapy.

Methods

We studied 27 children and young adults with either ND-LCH verified by structural magnetic resonance imaging (MRI) (group 1) or specific risk factors for (diabetes insipidus, craniofacial bone lesions), but no evidence of, neurodegenerative MRI changes (group 2). All patients underwent clinical, neurophysiological and MRI studies.

Results

Seventeen patients had MRI alterations typical for ND-LCH. Nine showed neurological impairment but only three were symptomatic; 11 had abnormal somatosensory evoked potentials (SEPs), and five had abnormal brainstem auditory evoked potentials (BAEPs). MR spectroscopy (MRS) showed reduced cerebellar NAA/Cr ratio in nine patients. SEPs showed sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for predicting ND-LCH of 70.6% (95%CI, 44.0%-89.7%), 100% (69.2%-100%), 100% (73.5%-100%), and 66.7% (38.4%-88.2%), respectively. Repeated investigations in group 1 revealed increasingly abnormal EP parameters, or neurological examination, or both, in nine of fifteen patients while MRI remained unchanged in all but one patient.

Conclusion

A targeted MRI study should be performed in all patients with risk factors for ND-LCH for early identification of demyelination. The combined use of SEPs and careful neurological evaluation may represent a valuable, low-cost, well-tolerated and easily available methodology to monitor patients from pre-symptomatic to symptomatic stages. We suggest a multidisciplinary protocol including clinical, MRS, and neurophysiological investigations to identify a population target for future therapeutic trials.

[Neuroimaging of Langerhans cell histiocytosis in the central nervous system of children]

Langerhans cell histiocytosis (LCH) is a rare disease characterized by the accumulation within tissues of anomalous dendritic cells similar to Langerhans cells. The clinical presentation varies, ranging from the appearance of a single bone lesion to multisystemic involvement. Central nervous system (CNS) involvement, manifesting as diabetes insipidus secondary to pituitary involvement, has been known since the original description of the disease. Two types of CNS lesions are currently differentiated. The first, pseudotumoral lesions with infiltration by Langerhans cells, most commonly manifests as pituitary infiltration. The second, described more recently, consists of neurodegenerative lesions of the CNS associated with neurologic deterioration. This second type of lesion constitutes a complication of the disease; however, there is no consensus about the cause of this complication. Our objective was to describe the radiologic manifestations of LCH in the CNS in pediatric patients.

Solitary Langerhans cell histiocytosis of frontal lobe: a case report and literature review

The brain parenchymal Langerhans cell histiocytosis (LCH) without systemic disease or lytic skull lesions is extremely rare. We report a 23-year-old male presenting with new onset 1 hour seizure with loss of consciousness 20 days prior to admission, and recurrent seizure 2 weeks later. Brain magnetic resonance imaging (MRI) showed an irregularly mass with enhancement involving the right frontal lobe. Microscopically, the lesion was characterized by sheets of Langerhans cells in addition to reactive inflammatory elements. Immunohistochemically, Langerhans cells were positive for Langerin, CD1a and S-100 protein. The patient received no chemotherapy or radiotherapy after surgery. After 24 months of follow-up, no recurrence or other systemic lesions were observed. Although there is no standard treatment for solitary cerebral LCH, the prognosis generally appears to be good.

Langerhans cell histiocytosis in children born 1982-2005 after in vitro fertilization

AIM

In a recent Swedish study, comparing data from the Swedish Cancer Register with the Medical Birth Register including data on IVF, an increased risk of Langerhans cell histiocytosis (LCH) was found in children born 1982-2005 after IVF. Here, we aimed to verify the LCH diagnoses and examine whether any special forms of the disease were overrepresented in this population.

METHODS

Medical records for all children with LCH conceived by IVF were acquired and the diagnosis confirmed or discarded. Disease characteristics were compared with data from children diagnosed with LCH 1992-2001 in the Stockholm County.

RESULTS

We verified LCH in seven children born after IVF, all born prior to 2002. These children did not have milder disease forms. The odds ratio (OR) to develop LCH for the whole group born after IVF was 3.2 [95% confidence interval (CI), 1.4-7.3] and for children born before 2002, 5.2 [95% CI, 2.3-11.9], compared with children in Stockholm County 1992-2001.

CONCLUSION

LCH was overrepresented in children born after IVF prior to 2002. Affected children did not have milder disease forms. These findings may be valuable to understand LCH aetiology. Additional studies on a putative correlation between IVF and LCH in the offspring are encouraged.