Recent advances in Langerhans cell histiocytosis

Langerhans Cell Histiocytosis Mimicking a Meningeal Lesion with Temporal Bone and Muscle Compromise in an Adult Patient: A Case Report

Introduction  Langerhans cell histiocytosis (LCH) is a rare proliferative systemic disease characterized by the growth of abnormal dendritic cells and wide-ranging organ involvement. This condition can affect individuals of all ages, but most commonly children, with a peak incidence in toddlers. Symptoms may vary depending on the affected organ or system. Case Report  A 43-year-old man presented with a left temporal stabbing headache unresponsive to management with therapy and nonsteroidal anti-inflammatory drugs. Initial evaluation revealed a contrast-enhanced left temporal extra-axial lesion with bone and muscle compromise. Differential diagnoses, including multiple myeloma, were explored. Initial laboratory tests and imaging studies showed no other abnormalities, except for splenomegaly and a residual granuloma in the left lung. En bloc resection of the lesion was recommended. The patient underwent surgical intervention, which included resection of the dural lesion and all borders of an infiltrating tumor within the temporalis muscle and the affected portion of the left temporal bone. Posterior pathological examination revealed LCH. Postoperative course was uneventful. Follow-up appointments were scheduled after pathology results confirmed the diagnosis. Patient has continued follow-up for the following 3 months after the surgical procedure. Further evaluations are pending. Discussion  This case report corresponds to a patient with LCH. These patients are individualized and stratified based on local or systemic involvement to determine the most appropriate type of management. This is a rare case as LCH is rare in older patients and the initial presented lesion initially mimicked a meningioma; however, its atypical behavior and associated lytic compromise led to consideration of possible differential diagnoses. Conclusion  LCH can present with lytic bone lesions, mimicking other conditions, including infiltrative neoplastic lesions. Early diagnosis and appropriate surgical management are essential for optimal patient outcomes. Long-term follow-up is crucial to monitor disease progression and response to treatment.

[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.

Cerebellar peduncle damage in Langerhans cell histiocytosis-associated neurodegenerative disease revealed by diffusion tensor imaging

PURPOSE

To confirm the hypothesis that brain white matter damage is involved in the pathogenesis and disease progression of Langerhans cell histiocytosis (LCH)-associated neurodegenerative disease (ND), we aimed to analyze pediatric patients with LCH using diffusion tensor imaging (DTI).

METHODS

We enrolled 33 patients with LCH and obtained 33 DTI datasets. Using DTI-based tractography, fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusivity (AD), and radial diffusivity (RD) were measured in the cerebral and cerebellar white matter tracts. The participants were divided into three groups-non-ND, ND without clinical symptoms (r-ND), and ND with clinical symptoms (c-ND)-according to their clinical status during the examination with DTI. We compared the DTI parameters in white matter tracts were compared among the three groups.

RESULTS

In the order of non-ND, r-ND, and c-ND groups, the FA in superior cerebellar peduncle (SCP) and middle cerebellar peduncle (MCP) significantly decreased, the ADC, AD, and RD of MCP, and the RD of SCP were significantly elevated (FA-SCP; p < 0.001, FA-MCP; p = 0.026, ADC-MCP; p < 0.001, AD-MCP; p = 0.002, RD-MCP; p = 0.003, and RD-SCP; p = 0.018). Furthermore, in the simple linear regression analysis, the FA, ADC, AD, and RD values in the MCP and the FA value in the SCP were significantly influenced by the presence of neurological symptoms and ND findings on MRI (all p < 0.001).

CONCLUSION

In LCH-ND, we identified microstructural damage in the SCP and MCP. DTI parameters in these tracts may help monitor LCH-ND; therefore, future studies are required to validate these results in a large cohort.

A case of neurodegenerative Langerhans cell histiocytosis exhibiting high osteopontin in cerebrospinal fluid without specific radiological abnormalities

Neurodegenerative Langerhans cell histiocytosis (ND-LCH) manifests several years after onset of LCH, with progressive neurological symptoms and characteristic brain imaging features. Although ND-LCH has a dismal neurological prognosis, distinct treatment strategies are not available owing to the unknown pathophysiology. We describe the case of a 6-year-old boy who developed left convergent strabismus four years after onset of multisystem LCH (MS-LCH). Although radiological imaging showed no abnormalities, the osteopontin level in the cerebrospinal fluid (CSF-OPN) was highly elevated without other abnormal CSF findings, leading to a diagnosis of ND-LCH. The patient received monthly intravenous immunoglobulin therapy for four years, without symptoms worsening. To investigate the relevance of OPN levels in LCH, we retrospectively analyzed serum and CSF OPN levels in eight LCH patients. Serum OPN levels were markedly elevated in the two MS-LCH patients with macrophage activation (400 and 445 ng/mL) compared to the other six patients (mean: 59 ng/mL). CSF-OPN levels were elevated in the ND-LCH patient (620 ng/mL) compared to the two patients with pituitary involvement (160 and 182 ng/mL), suggesting that the pathophysiology of ND-LCH reflects its inflammatory status. Analysis of CSF-OPN levels would be a useful tool to detect and treat ND-LCH.

Serum levels of soluble interleukin 2 receptor (sIL-2R), tumor necrosis factor-alpha (TNF-α), and immunoglobulin M are correlated with the disease extent in childhood Langerhans cell histiocytosis

PURPOSE

This study aimed to identify peripheral parameters associated with the severity of Langerhans cell histiocytosis (LCH) and to look for indicators associated with improvement in LCH patients with risk-organ involvement.

METHODS

This study enrolled LCH patients who were assessed as active disease-better (AD-B) after treatment. Patients were divided into the single system (SS) group, multisystem disease without risk-organ involvement (RO- MS) group, and multisystem disease with risk-organ involvement (RO + MS) group. Serum cytokines, immunoglobulins, and lymphocyte subsets were measured at admission for all three groups. Changes in these indicators after treatment were also analyzed.

RESULTS

From January 2015 to January 2022, a total of 46 patients were recruited in the present study, including 19 patients (41.3%) in the SS group, 16 patients (34.8%) in the RO- MS group, and 11 patients (23.9%) in the RO + MS group. Serum levels of soluble interleukin 2 receptor (sIL-2R) (> 912.5 U/mL), tumor necrosis factor-alpha (TNF-α) (> 20.3 pg/mL), and immunoglobulin M (< 1.12 g/L) were found to be effective in identifying patients in the RO + MS group. Furthermore, the levels of sIL-2R (SS vs RO + MS: P = 0.002, RO- MS vs RO + MS: P = 0.018) and CD8 + T-cell count (SS vs RO + MS: P = 0.028) significantly declined in the RO + MS group after treatment, indicating disease improvement.

CONCLUSIONS

The levels of sIL-2R and TNF-α were positively correlated with the extent of disease, while the levels of IgM were negatively correlated with the extent of disease. Additionally, the levels of sIL-2R and CD8 + T-cell count could serve as useful indicators to evaluate the treatment response in RO + MS-LCH patients.

Cladribine and cytarabine in children refractory high risk multisystem Langerhans cell histiocytosis

There is no uniform regimen for refractory Langerhans cell histiocytosis (LCH). We retrospectively described patients with refractory multisystem and risk organ involvement LCH treated with the low-dose (Ara-c, 100 mg/m2/d × 5day; 2-CDA, 5 mg/m2/d × 5day) chemotherapy (LDC) and the intermediate-dose (Ara-c, 500 mg/m2/d × 5day; 2-CDA, 9 mg/m2/d × 5day) chemotherapy (IDC). 26 patients and 10 patients receiving the LDC and IDC regimen from January 2013 to December 2016 were included in the study. The overall response rate exhibited no significant difference between the LDC and IDC groups after four courses (76.9% vs 90%, P = 0.375) and eight courses (80.8% vs 100%, P = 0.135) of treatment. No statistical differences in the overall survival rate were observed between the two groups, but 5-year event-free survival rate of patients in the IDC group was higher than that in the LDC group at the median follow-up of 6.16 and 5.07 years (88.9% vs 52.9%, P = 0.033). The patients in the IDC group had more severe myelosuppression than those in the LDC group (grade 3/4 myelosuppression, 80% vs 19.2%, P = 0.001). The intermediate-dose regimen of 2CDA and Ara-c had a higher event-free survival rate and a similar overall survival rate compared with the low-dose regimen.

Intensification of treatment with vinca alkaloid does not improve outcomes in pediatric patients with Langerhans cell histiocytosis: results from the JPLSG LCH-12 study

Chemotherapy with cytarabine, vincristine (VCR), and prednisolone has achieved low mortality rates in pediatric patients with Langerhans cell histiocytosis (LCH). However, relapse rates remain high, making event-free survival (EFS) rates unsatisfactory. A nationwide clinical trial, LCH-12, tested a modified protocol in which the early maintenance phase was intensified with increasing dosages of VCR. Patients newly diagnosed with multifocal bone (MFB) or multisystem (MS) LCH and aged < 20 years at diagnosis were enrolled between June 2012 and November 2017. Of the 150 eligible patients, 43 with MFB were treated for 30 weeks and 107 with MS LCH were treated for 54 weeks. One patient with MS LCH died of sepsis during the induction phase. The 3-year EFS rates among patients with MFB LCH, risk organ (RO)-negative MS LCH, and RO-positive MS LCH were 66.7% (95% confidential interval [CI], 56.5-77.0%), 66.1% (95% CI 52.9-76.4%), and 51.1% (95% CI 35.8-64.5%), respectively, similar to previously observed rates. EFS rates were significantly lower in patients with disease activity scores > 6 than in those with scores ≤ 6. The strategy that included more intense treatment with VCR was not effective. Other strategies are required to improve outcomes in patients with pediatric LCH.

Relapses of multisystem/multifocal bone Langerhans cell histiocytosis in paediatric patients: Data analysis from the JLSG-96/02 study

We assessed relapse patterns in paediatric patients with relapsed Langerhans cell histiocytosis (LCH) who were initially treated with the JLSG-96/02 protocol. We analysed 187 relapse events in 101 relapsed LCH patients [31 with multifocal bone (MFB) and 70 with multisystem (MS) at LCH diagnosis] among a total 317 patients enrolled in JLSG-96/-02 studies. Relapse of LCH was defined as an exacerbation of the non-active disease (NAD) condition. Of the 317 patients, 101 (31.9%) had the first relapse at 1.5 years after initiation of therapy. The first relapse and subsequent relapses did not differ between patients with MFB and MS disease. Of the 187 relapse events, relapse occurred as a single-system disease (n = 159; 85%), in which isolated bone relapse (n = 104; 55%) was the most common. Relapse at MS disease with the risk of organ involvement is extremely rare. After relapse(s), most patients underwent chemotherapy (122/187; 65%) and 87% of them achieved NAD status again. The incidence of permanent consequences was significantly higher in patients with relapses than in those without relapses. In the JLSG cohort, bone relapse most occurred in both MFB and MS patients. Most relapses could be effectively controlled by repeated administration of the initial chemotherapy.

Langerhans Cell Histiocytosis in Children: Literature Review

Relevant information on Langerhans cell histiocytosis development and course in children is presented. The current concepts of disease pathogenesis, principles of its severity evaluation, patients stratification into risk groups, as well as of clinical course features are described. Modern approaches to the disease treatment via targeted therapy are summarized and analyzed. 

Outcomes of liver transplantation in children with Langerhans cell histiocytosis: Experience from a quaternary care center

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare but important cause of end-stage liver disease in children. Conventional chemotherapeutic agents that are otherwise the standard-of-care in LCH may be counterproductive in patients with hepatic decompensation. Furthermore, the precise role of liver transplantation (LT) in the management of LCH remains unclear.

METHODS

Review of a prospectively collected database (January 2014 to December 2020) of children with liver disease was performed. All clinical details of patients with LCH managed at our center were collected and data analyzed. Based on the outcomes, a management algorithm was proposed.

RESULTS

Of the eight (five male) patients referred to our unit, six (75%) underwent LT (four and two for compensated and decompensated cirrhosis, respectively). Median age at diagnosis of LCH was 25 (range: 9-48) months. Two patients, who had previously completed LCH-specific chemotherapy, underwent upfront LT for compensated cirrhosis. Other two patients with compensated cirrhosis showed evidence of active disease. They underwent LT following completion of chemotherapy. Two children with decompensated cirrhosis also had evidence of active disease and were started on modified chemotherapy Both of them had progression of liver disease while on chemotherapy. Hence, an urgent LT was performed which was followed by completion of chemotherapy in these patients. On a median follow-up of 30.5 (10.5-50) months, all post-LT patients were alive with stable graft function and showed no disease recurrence.

CONCLUSION

We demonstrate that an algorithmic approach, along with newer chemotherapeutic agents, results in excellent outcomes in LCH patients with liver involvement. Larger multicentric studies on this rare disease are, however, needed to validate our findings.

Pilot study to estimate the safety and effectiveness of hydroxyurea and methotrexate recurrent langerhans cell histiocytosis (LCH-HU-pilot)

This study was a non-blinded, multicenter, single-arm study. Recurrent (relapsed) LCH is defined as the appearance of new lesions or the enlargement of preexisting lesions due to LCH. In this study, all patients received hydroxyurea, and if the treatment response was unsatisfactory, methotrexate was added. The duration of treatment was 48 weeks. The primary endpoint was the rate of non-active disease achievement, which was 24 weeks after initiating hydroxyurea administration. No active disease is defined as the resolution of all the signs and symptoms related to LCH.

BRAF-V600E utilizes posttranscriptional mechanisms to amplify LPS-induced TNFα production in dendritic cells in a mouse model of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory disease characterized by abnormal dendritic cells (DCs) with hyperactive ERK signaling, called "LCH cells." Since DCs rely on ERK signaling to produce inflammatory molecules in response to pathogenic cues, we hypothesized that hyperactive ERK enhances DCs inflammatory responses. We specifically investigated TLR4-induced TNFα production in LCH cells by utilizing the BRAF-V600Efl/+ :CD11c-Cre mouse model of LCH, which hyperactivates ERK in DCs. We measured LPS-induced TNFα production both in vivo and in vitro using splenic CD11c+ cells and bone marrow-derived DCs with or without pharmacologic BRAFV600E inhibition. We observed a reversible increase in secreted TNFα and a partially reversible increase in TNFα protein per cell, despite a decrease in TLR4 signaling and Tnfa transcripts compared with controls. We examined ERK-driven, posttranscriptional mechanisms that contribute to TNFα production and secretion using biochemical and cellular assays. We identified a reversible increase in TACE activation, the enzyme required for TNFα secretion, and most strikingly, an increase in protein translation, including TNFα. Defining the translatome through polysome-bound RNA sequencing revealed up-regulated translation of the LPS-response program. These data suggest hyperactive ERK signaling utilizes multiple posttranscriptional mechanisms to amplify inflammatory responses in DCs, advancing our understanding of LCH and basic DC biology.

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.

Infantile-Onset Isolated Neurohypophyseal Langerhans Cell Histiocytosis with Central Diabetes Insipidus: A Case Report

Central diabetes insipidus (CDI) is a rare disease in children and has a variety of etiologies. The major causes of CDI with pituitary stalk thickening (PST) are germinoma, Langerhans cell histiocytosis (LCH), and Lymphocytic infundibulo-neurohypophysitis, which are difficult to differentiate by imaging and require pathological diagnosis. We report a case of infantile-onset isolated neurohypophyseal LCH diagnosed by pathological findings. A 2-year-old girl presented with polydipsia and polyuria. CDI was diagnosed and treatment with oral desmopressin was initiated. Magnetic resonance imaging (MRI) of the head showed PST and absence of high-signal intensity of posterior pituitary on T1-weighted images. Follow-up MRI scans showed that the tumor mass was gradually increasing and extending posteriorly toward the area near the mamillary body. Simultaneously, anterior pituitary dysfunction was observed. She underwent a biopsy of the PST and LCH was diagnosed by immunohistochemical analysis. DNA analysis showed no BRAF V600E mutation. Monotherapy with 2-Chlorodeoxyadenosine reduced the tumor size but did not improve pituitary function. Isolated neurohypophyseal LCH should be considered in infantile-onset cases of CDI with PST. 2-CdA treatment resulted in rapid PST shrinkage. Further cases are needed to determine whether early diagnosis and treatment can prevent anterior pituitary dysfunction.

Progressive destruction of jaws caused by the delayed treatment of Langerhans cell histiocytosis in a 2-year-old boy: A case report

Langerhans cell histiocytosis (LCH) is a disease with varied clinic manifestations. The oral symptoms and signs of LCH localized to the jaws are nonspecific, which may lead to misdiagnosis of this disease. The purpose of this paper was to present the case of a 2-year, 4-month-old LCH patient with progressive destruction of jaws caused by the delayed treatment due to the global outbreak of COVID-19. The cone beam CT analysis after an interval of 6 months reminded us the great significance of early diagnosis and treatment of LCH.

Adult Langerhans Cell Histiocytosis and the Skeleton

Langerhans cell histiocytosis (LCH) is a rare inflammatory neoplasia in which somatic mutations in components of the MAPK/ERK pathway have been identified. Osseous involvement is evident in approximately 80% of all patients and may present as a single osteolytic lesion, as a multi-ostotic single system disease or as part of multisystem disease. Both exogenous, such as treatment with glucocorticoids, and endogenous parameters, such as anterior pituitary hormone deficiencies and inflammatory cytokines, may severely affect bone metabolism in LCH. Computed tomography (CT) or magnetic resonance imaging (MRI) are usually required to precisely assess the degree of bone involvement; 18F-fluorodeoxyglucose (FDG) positron emission tomography-CT can both detect otherwise undetectable LCH lesions and differentiate metabolically active from inactive or resolved disease, while concomitantly being useful in the assessment of treatment response. Treatment of skeletal involvement may vary depending on location, extent, size, and symptoms of the disease from close observation and follow-up in unifocal single-system disease to chemotherapy and gene-targeted treatment in cases with multisystem involvement. In any case of osseous involvement, bisphosphonates might be considered as a treatment option especially if pain relief is urgently needed. Finally, a patient-specific approach is suggested to avoid unnecessary extensive surgical interventions and/or medical overtreatment.

Second-line regimen for CNS-involved pediatric Langerhans cell histiocytosis

PURPOSE

Langerhans cell histiocytosis (LCH) can affect any organ. Central nervous system (CNS) involvement is rare, and its management is poorly understood. This study aimed to analyze the clinical response and prognosis of pediatric LCH with central diabetes insipidus (CDI) treated with second-line therapy with cytarabine (Ara-c), cladribine (2-cdA), dexamethasone, and vindesine.

METHODS

This retrospective case series study included pediatric LCH with CDI treated at Beijing Children's Hospital affiliated with Capital Medical University (11/2012-01/2018). After the first-line 2009-LCH regimen, patients with active disease/worse response, relapse, or no significant improvement in risk organs, pituitary, or lung were given the second-line therapy. Baseline characteristics, clinical response and adverse reactions were observed.

RESULTS

Twenty-six children with CDI and disappearance of hyperintensity in the posterior pituitary were included. They received "Regimen A" Ara-c + dexamethasone + vindesine (n = 7) or "Regimen B" Ara-c + dexamethasone + vindesine + 2-cdA (n = 19) as second-line therapy. There were 14 patients with CDI but without pituitary stalk thickening (PST) and 12 with CDI and PST. In patients with CDI alone, 4/4 patients receiving Regimen A and 3/10 receiving Regimen B improved. All patients with CDI and PST showed improvement for PST. The reappearance of hyperintensity at the posterior pituitary was observed in 10 patients with CDI. All 26 children were alive after a median follow-up of 40.5 months. There were no chemotherapy-related deaths.

CONCLUSION

A combined therapy with Ara-c, 2-cdA, dexamethasone, and vindesine could partially alleviate pituitary disease conditions in pediatric LCH with CNS involvement, with good tolerance.

Bone lesions of Langerhans cell histiocytosis triggered by trauma in children

BACKGROUND

Bone lesions of Langerhans cell histiocytosis (LCH) may be triggered by trauma.

METHODS

The characteristics of pediatric patients in the JLSG-02 study cohort who developed a bone lesion at the trauma site at diagnosis of LCH were analyzed retrospectively.

RESULTS

Of the 261 pediatric patients with LCH, 12 (4.6%), of median age 4.9 years, had trauma-triggered bone LCH lesions at diagnosis, making them significantly older than the remaining patients (P = 0.006). Trauma sites included the craniofacial regions in 10 patients and the lumbar spine and pelvis in one patient each. At the time of trauma, six patients had a bump at the site, whereas none had extradural hematomas or bone fractures. The median time from trauma to onset was 4 weeks. Of these 12 patients, three had isolated bone (IB) disease; four had multifocal bone (MFB) disease, including the bone lesion at the trauma site; and five had multisystem disease, including four with lesions in neighboring tissue and one with polyuria (posterior pituitary lesion) more than 1 year before the trauma-triggered bone lesion. Treatment responses were good in all 12 patients and none died, but relapses were observed in two patients, one each with IB and MFB disease.

CONCLUSIONS

About 5% of pediatric patients with LCH developed new trauma-triggered bone lesions at a relatively old age. These lesions can manifest as IB, or, in patients with underlying LCH diseases, as MFB or multisystem. Good clinical outcomes were observed in these patients.

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

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.

Central diabetes insipidus developing in a 6-year-old patient 4 years after the remission of unifocal bone Langerhans cell histiocytosis

A six-year-old boy was referred with a one-and-a-half months history of polyuria and polydipsia. At the age of two, he had a single lytic bone lesion in his femoral head, diagnosed as Langerhans cell histiocytosis (LCH) by biopsy at another hospital. As no other affected organs were detected and the affected bone lesion was self-limited, he was not followed up afterward and was doing well. He was diagnosed with diabetes insipidus (DI) by confirming hypernatremia (Na: 148 mEq/l) with hyperosmolar serum (s-Osm 298 mOSM/kg) and inappropriately diluted urine (u-Osm 205 mOSM/kg). His polyuria and polydipsia improved dramatically using the perioral diuretic hormone, and other pituitary functions were not impaired. Magnetic resonance imaging revealed an enlarged pituitary stalk. Sensitive and specific biomarkers of germ cell tumors, including alpha-fetoprotein, placental alkaline phosphatase, and β-hCG in the cerebrospinal fluid, were not detected, indicating relapse of LCH. Genetic analysis revealed a BRAF V600E mutation in the primary bone lesion. We recommend systematic follow-up of patients with a history of LCH, even non-CNS single-system single-site disease, especially with BRAF V600E mutation.

Immune Microenvironment in Langerhans Cell Histiocytosis: Potential Prognostic Indicators

In this study, the immune microenvironment in Langerhans cell histiocytosis (LCH) was characterized to determine if immune indices are predictive of severity. Serum samples from 54 treatment-naïve patients were analyzed quantitatively for inflammatory cytokines and immunoglobulins before and after the induction of chemotherapy. The initial serum sIL-2R, TNF-α, and IL-10 of untreated LCH patients with risk organ involvement (RO+) were significantly higher than those with single-system (SS) involvement. LCH patients with hematologic involvement exhibited a significantly higher sIL-2R, TNF-α, IL-10, and IL-1β expression, as compared to the group without involvement. sIL-2R, TNF-α, and IL-10 were increased in patients with liver or spleen involvement. Th cells have decreased in the liver+ and spleen+ group, and Ts cells were significantly decreased in non-response group after induction chemotherapy. The serum level of immune indices represents, to some extent, the severity of the disease. Pertinent laboratory inspections can be used to improve risk stratification and guide immunotherapy.

Langerhans cell histiocytosis: A diagnostic enigma in the oral cavity

Langerhans cell histiocytosis (LCH) is a rare reactive and proliferative disease of histiocytes. The disease occurs predominantly in children and rarely in adults. This disease of unknown etiology exhibits extreme clinical heterogeneity. Even though LCH manifests initially in the oral cavity in most of the cases, owing to the relative rarity of the condition, it remains a disease in which the diagnosis is often delayed, missed or misdiagnosed. This is a case of LCH in a child which presented with swelling in the mandibular region.

Combination of Neoadjuvant Therapy and Liver Transplantation in Pediatric Multisystem Langerhans Cell Histiocytosis With Liver Involvement

Background: Langerhans cell histiocytosis (LCH) is characterized by misguided myeloid differentiation, whose prognosis was poor with involvement of risk organs. Remaining issues include how to improve the outcomes of patients with risk-organ involvement.

Methods: A retrospective study was conducted in Renji Hospital exploring the effects of neoadjuvant therapy in combination with pediatric liver transplantation (LT) for LCH patients based on data collected between October 2006 and October 2019.

Results: We presented here five cases of multisystem LCH patients underwent systemic chemotherapy to control active lesions, followed by LT to treat end-stage liver diseases. Manifestations before LT included elevated transaminase levels (n = 5, 100%), jaundice (n = 4, 80%), ascites (n = 3, 60%), and variceal hemorrhage (n = 1, 20%). Three patients underwent orthotopic liver transplantation (OLT) and two underwent living donor liver transplantation (LDLT). Until December 2019, median follow-up time was 32 months (range, 2–67 months). Liver functions significantly improved compared with pre-operative conditions. One patient had perioperative hepatic artery complications and one patient had a recurrence in the lung. EBV infection occurred in four (80%) patients and CMV infection occurred in one (20%). There was one case of drug-induced liver injury diagnosed on biopsy 13 months after LT. None underwent re-transplantation and there were no rejection or portal vein and biliary complications.

Conclusion: Combination of neoadjuvant therapy and LT is an effective paradigm in treatment of multisystem LCH with severe liver dysfunction. With advances in chemotherapy regimen for multisystem LCH and LT surgery, perspectives on prognosis for LCH children are promising.

BRAF V600E-Positive Congenital Multisite Langerhans Cell Histiocytosis

Congenital Langerhans cell histiocytosis (LCH) usually manifests as a disease limited to the skin, with self-healing characteristics; however, in some cases, it may be a more severe entity, with multisystemic expression and poor prognosis. We present the case of a patient diagnosed with multisystemic congenital LCH, with the presence of the BRAF V600E mutation, with a severe form of the disease, with risk organ compromise, and manifestations of resistance to chemotherapy. This case is a challenge due to the disease's biologically aggressive behavior in this patient. It presents unique treatment difficulties as a result of inherent resistance to conventional therapy and uncertain response to BRAF inhibitors.

Congenital Langerhans cell histiocytosis

Langerhans cell histiocytosis is a rare pathology with different clinical manifestations in the neonatal period ranging from isolated bone lesions to systemic compromise. We report a case of Langerhans cell histiocytosis including a literature review focused on the clinical manifestations, diagnosis, and treatment. A one-month-old patient was brought to medical consultation with lymphadenopathy and skin lesions, which were initially managed as an infectious pathology. The disease continued its progression without improvement with the treatment until the patient died due to respiratory failure. The lymph node and skin biopsies revealed infiltration of atypical cells with positive immunohistochemistry for S100, CD1, and CD68 confirming Langerhans cell histiocytosis. This disorder represents a great challenge and, therefore, it is important to alert and sensitize medical teams about it for timely diagnosis and management.

Primary Oro-Facial Manifestations of Langerhans Cell Histiocytosis in Pediatric Age: A Bi-Institutional Retrospective Study on 45 Cases

Aims: Langerhans Cell Histiocytosis is a rare hematologic disorder usually affecting children and most commonly involving the head and neck region. Primary oro-facial manifestations are rare, and their diagnosis is often challenging as they are numerous and often resemble common pathologies, refractory to conventional medical and/or instrumental treatments. For such reasons, the diagnosis is frequently delayed, as is the following staging and therapy onset. We retrospectively studied 45 pediatric patients affected by Langerhans Cell Histiocytosis with onset in the head and neck, to examine their clinical and radiological features at the early stage. Materials and Methods: The study was a retrospective bi-institutional analysis (Department of Pediatric Dentistry and Pediatric Oncology of “Sapienza” University of Rome, Department of Interdisciplinary Medicine of the University of Bari “Aldo Moro”), which enrolled 45 patients (age range 0–18 year-old) affected by Langerhans Cell Histiocytosis with oro-facial onset. Data regarding clinical appearance, number, site, synchronous or metachronous occurrence, involved tissues/organs, radiographic features and clinical outcomes were collected, listed and overall differentiated by two age ranges (0–10-year-olds and 10–18-year-olds). Results: Patients were 26 males and 19 females, with an average age at the time of diagnosis of 4.8 ± 3.8 years (median = 3.9 years). The most common findings were inflamed, hyperplastic, painful and often ulcerated gingival lesions (22 cases), associated with deciduous tooth mobility and/or dislocation with bone loss in 18 cases, followed by nine single eosinophilic granulomas of the mandible and two of the maxilla. Lesions of the palatal mucosa were observed in six patients; nine patients showed on radiograms the characteristic “floating teeth” appearance in the mandible with synchronous lesions of the maxilla in six. Paresthesia was relatively un-frequent (three cases) and the pathological fracture of the mandible occurred in six. Head/neck lymph nodes involvement was associated with oral lesions in 12 cases and skull lesions in 14. Otitis (media or externa) was detected in four instances, exophthalmia in two, cutaneous rush in nine, contextual presence or subsequent onset of insipidus diabetes in eight. As for therapy, single or multiple small jaw lesions were all surgically removed; chemotherapy with vinblastine alone or associated with corticosteroids was the principal treatment in almost the 80% of cases; more than 50% of patients received corticosteroids, while only three patients received adjunctive radiotherapy. The overall mortality account for less than 9% (four of 45 cases) and recurrence observed in eight patients after therapy. Conclusions: Langerhans Cell Histiocytosis may mimic several oro-facial inflammatory and neoplastic diseases. Considering the potential disabling sequela following head and neck localization of Langerhans Cell Histiocytosis in children, especially at the periodontal tissues with teeth and alveolar bone loss, lesion recognition along with the histological examination of suspicious tissues is mandatory to achieve an early diagnosis and to prevent further organ involvement.

Effective rescue treatment with vemurafenib of an infant with high-risk Langerhans cell histiocytosis

INTRODUCTION

The recently identified role of a BRAF somatic mutation in the pathophysiology of Langerhans cell histiocytosis (LCH) offers new therapeutic options. Herein we describe the case of a 10-month-old infant with refractory high-risk LCH successfully treated with vemurafenib.

OBSERVATION

The patient first presented with cutaneous LCH at the age of 2 months. The disease remained undiagnosed until she was 6 months old, when it rapidly evolved to a multisystemic high-risk and life-threatening disease, refractory to 2 lines of chemotherapy. BRAFV600E mutation was found at skin biopsy, and targeted therapy with vemurafenib was started when she was 10 months old. The treatment induced a fast and sustained response, but rapid relapse occurred after treatment discontinuation, leading to resumption of treatment, once more resulting in a sustained response.

CONCLUSION

Our case highlights the first-line role of dermatologists in establishing the diagnosis of LCH, especially in children, in whom the eruption may be difficult to identify, leading to delayed diagnosis. Targeted therapy with vemurafenib has recently been described in children in this indication and our results support its efficacy, highlighting the need for prolonged treatment and raising the question of maintenance therapy, as well as the necessity for large-scale and long-term studies.

Analysis of the BRAF and MAP2K1 mutations in patients with Langerhans cell histiocytosis in Japan

In Langerhans cell histiocytosis (LCH), somatic gene mutations in the mitogen-activated protein kinase pathway have been identified in more than 80% of cases in Western countries, in which mutually exclusive BRAF and MAP2K1 mutations are involved. Among them, BRAF V600E mutation is the major contributor (50-60%). In 59 patients (50 children and nine adults) with LCH (not including pulmonary LCH) in Japan, we first screened for BRAF V600E in all patients followed by target sequencing for other gene mutations in 17 of BRAF V600E-negative patients. As a result, BRAF V600E mutation was detected in 27/59 (46%) patients. We also identified BRAF mutations other than V600E in five and MAP2K1 mutations in nine patients. Thus, gene mutations in BRAF or MAP2K1 were identified in 41/44 (93%) of the fully tested patients. Regarding the correlation of clinical features and genotype in pediatric patients, we found that BRAF V600E mutation status was not correlated with sex, age at diagnosis, disease extent, response to first-line therapy, relapse, or CNS-related sequelae. Interestingly, MAP2K1 exon 2 in-frame deletion was related to the risk organ involvement; however, further studies are required to clarify the impact of these gene mutations on the clinical features of patients with LCH.

Long-term outcomes of children with extracutaneous juvenile xanthogranulomas in Japan

BACKGROUND

Juvenile xanthogranuloma (JXG) is the most common non-Langerhans cell histiocytosis in children. The mortality and morbidity of JXG with extracutaneous lesions remain unclear.

METHODS

Data of patients aged < 18 years who were diagnosed with JXG between 2001 and 2010 were retrospectively collected through a nationwide survey.

RESULTS

Twenty patients (11 male and nine female) had extracutaneous lesions. The median observation time was 10 years (range, 0-17). Six patients presented with symptoms at birth. The median age at diagnosis was 8.5 months (range, 0 month-13 years). Fifteen patients underwent treatment for JXG, including chemotherapy (n = 11), and five did not receive treatment. All patients except one survived; 17 were disease-free and two survived with disease. One newborn-onset patient with liver, spleen, and bone marrow involvement died of the disease. Permanent sequelae included central diabetes insipidus, growth hormone deficiency, and panhypopituitarism detected at diagnosis in three, one, and two patients, respectively. Four patients had visual impairment (optic nerve compression and intraocular invasion in two each), three had epilepsy, one had mental retardation, and one had a skin scar. Eight patients who had intracranial lesions were older at diagnosis, and had a higher frequency of disease-related comorbidities and permanent sequelae than those without intracranial involvement.

CONCLUSIONS

Patients with extracutaneous JXG had good outcomes, although those with intracranial lesions had serious permanent sequelae. Effective and safe treatment regimens for patients with intracranial JXG need to be developed.

Adult Langerhans cell histiocytosis of the central nervous system

Langerhans cell histiocytosis (LCH), a disorder characterized by aberrant function and proliferation of mononuclear phagocytic cells called Langerhans cells, usually occurs in those <15 years of age. Adult-onset LCH is extremely rare. We present a case of a 35-year-old woman who presented with multiple episodes of confusion, rapidly progressive cognitive decline, and multiple endocrinopathies, including diabetes insipidus. Brain imaging showed a hypothalamic lesion, and biopsy results confirmed the diagnosis of LCH. Given the wide variety of presentations and the multiple differential diagnoses of hypothalamic lesions, it is essential to be aware of this uncommon condition, especially in adults, where it may be underdiagnosed.

Langerhans cell histiocytosis confined to extrahepatic bile duct causing sclerosing cholangitis in child: a case report

Background

Langerhans cell histiocytosis (LCH) is an abnormal accumulation of Langerhans cells in various organs that sometimes induces organ dysfunction. LCH can affect the liver, resulting in sclerosing cholangitis and biliary cirrhosis. However, liver and bile duct involvement is usually observed in the disseminated form of LCH. We herein report a rare case of LCH localized only in the extrahepatic bile duct that resulted in severe liver cirrhosis.

Case presentation

A 3-year-old boy with elevated liver enzymes, obstructive jaundice, and dilation of the common bile duct was referred to our institution. Contrast-enhanced computed tomography showed atrophy of the right hepatic lobe, relative hypertrophy of the left hepatic lobe, choledocholiths, and biliary debris extensively with biliary duct dilation. Magnetic resonance cholangiopancreatography revealed dilation of the intrahepatic and extrahepatic bile ducts and multiple choleliths in the gallbladder and common bile duct. Laparoscopic cholecystectomy, intraoperative cholangiography, liver biopsy, and gastrointestinal fiberscopy were performed. A liver specimen showed severe biliary cirrhosis due to sclerosing cholangitis. The patient then underwent living-donor liver transplantation because of severe liver cirrhosis 3 months after the first surgery. The common bile duct was not suitable for duct-to-duct anastomosis and was resected because of severe inflammation. Histologic sections of the common bile duct showed histiocytic cell proliferation. Immunohistochemistry revealed histiocytoses that were positive for Langerin, S-100 protein, and CD1a. However, no histiocytic cell proliferation was noted in the liver tissue. The definitive diagnosis was LCH localized to the extrahepatic bile duct. LCH in the extrahepatic bile duct seemed to cause sclerosing cholangitis. The patient was discharged uneventfully 2 months after living-donor liver transplantation.

Conclusions

LCH localized to the extrahepatic bile duct is extremely rare; however, LCH can still affect the extrahepatic bile ducts on occasion. LCH should be considered as a differential diagnosis if pediatric patients show the presence of sclerosing cholangitis.

Paediatric pulmonary Langerhans cell histiocytosis

Paediatric pulmonary Langerhans cell histiocytosis (pPLCH) is a rare diffuse cystic lung disease. Unlike pulmonary Langerhans cell histiocytosis (LCH) in adults, which is often seen as an isolated condition with smoking being a major risk factor, isolated pPLCH is vanishingly rare in children and it is most often a component of multisystem LCH. Diagnosis should be based on histological and immunophenotypic examination of affected tissue in addition to clinical and radiological features. It should be considered an important differential for diffuse cystic lung disease in paediatric patients. Recent progress in the biological understanding of the disease supports the classification of LCH as an inflammatory myeloid neoplasia. Chemotherapy and specific management of respiratory complications are the mainstays of treatment. The lungs are no longer considered a "risk organ" in LCH as pulmonary involvement is not associated with a worse prognosis than the involvement of other organs. Multidisciplinary treatment approaches are needed. Prognosis can be good but is adversely influenced by multisystem involvement, and complications such as pneumothoraces and respiratory failure can be life threatening. This review aims to give an overview of this condition, with a focus on the diagnosis, monitoring and management of complications such as pneumothoraces and respiratory failure, which can be challenging for the paediatric respiratory specialist.

EDUCATIONAL AIMS

To give an overview of paediatric pulmonary LCH.To discuss the differential diagnosis of paediatric cystic lung disease.

Childhood Langerhans cell histiocytosis: a disease with many faces

BACKGROUND

Langerhans cell histiocytosis (LCH) is a group of diseases characterized by the proliferation and accumulation of Langerhans cells. Clinical presentations of LCH vary widely.

DATA SOURCES

A PubMed search was conducted using Clinical Queries with the key term "Langerhans cell histiocytosis". The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. This paper is based on, but not limited to, the search results.

RESULTS

Generally, patients with LCH can be divided into two groups based on the extent of involvement at diagnosis, namely, single-system LCH and multisystem LCH. The involvement may be unifocal or multifocal. Patients with isolated bone lesions typically present between 5 and 15 years of age, whereas those with multisystem LCH tend to present before 5 years of age. The clinical spectrum is broad, ranging from an asymptomatic isolated skin or bone lesion to a life-threatening multisystem condition. Clinical manifestations include, among others, "punched out" lytic bone lesion, seborrheic dermatitis-like eruption, erythematous/reddish-brown crusted/scaly papules/maculopapules/plaques/patches, and eczematous lesions, diabetes insipidus, hepatosplenomegaly, cytopenias, lymphadenopathy, and an acute fulminant disseminated multisystem condition presenting with fever, skin rash, anemia, thrombocytopenia, lymphadenopathy, and hepatosplenomegaly. The diagnosis is clinicopathologic, based on typical clinical findings and histologic/immunohistochemical examination of a biopsy of lesional tissue. Positive CD1a, S100, and/or CD207 (Langerin) immunohistochemical staining of lesional cells is required for a definitive diagnosis. Watchful waiting is recommended for patients with skin-only LCH. Patients with symptomatic or refractory skin-only LCH may be treated with topical tacrolimus/corticosteroids, topical nitrogen mustard, oral methotrexate, or oral hydroxyurea. The current recommended first-line therapy for patients with multisystem LCH is 12 months therapy with prednisone and vinblastine. Mercaptopurine is added for patients with risk organ involvements.

CONCLUSIONS

Because of the broad spectrum of clinical manifestations and the extreme diversity of disease, LCH remains a diagnostic dilemma. Morphological identification of LCH cells and positive immunochemical staining with CD1a, S100, and/or CD207 (Langerin) of lesional cells are necessary for a definitive diagnosis.

BRAF V600E Mutation: A Significant Biomarker for Prediction of Disease Relapse in Pediatric Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease presenting with usually a localized disease but sometimes a widespread aggressive disorder especially in children. Among the somatic mutations in RAF-MEK-ERK pathway, especially BRAF mutation has been detected so far in LCH. We aimed in this study to investigate the prognostic significance of the mutations of target genes playing a role in the RAF-MEK-ERK pathway in pediatric LCH. Mutation analyses were performed on tumor DNA extracted from formalin-fixed paraffin-embedded biopsy specimens of 38 pediatric LCH cases using a direct sequencing technique for BRAF, ARAF, MAP2K1, and MAP3K1 genes. The mutational status was correlated statistically with survival, clinical progression (disease relapse), and the established clinical prognostic parameters of LCH such as age, gender, localization, multisystem disease, central nervous system risk lesions, and risk organ or special-site involvement. BRAF V600E mutation was detected in 14 cases (36.8%), whereas ARAF mutation was found in only 1 case. No mutations were identified for MAP2K1 and MAP3K1 genes. The association of BRAF V600E mutation was significant in children with multisystem disease, younger age (<2 years), skin, and special organ involvement. BRAF V600E mutation was an independent predictive parameter for disease relapse. We therefore conclude that BRAF V600E mutation may be a significant marker for predicting disease progression in LCH and a candidate for targeted therapy for children with disease relapse and multisystem disease.

Successful treatment with 2-chlorodeoxyadenosine of refractory pediatric Langerhans cell histiocytosis with initial involvement of the gastrointestinal tract

Gastrointestinal (GI) tract involvement in Langerhans cell histiocytosis (LCH) is extremely rare. Langerhans cell histiocytosis with GI tract involvement (GI-LCH) is frequently associated with multi-system disease, and usually presents with severe systemic symptoms, such as protein-losing enteropathy (PLE). Although the GI tract is not included among the organs at risk, the prognosis of GI-LCH is poor, and no effective chemotherapeutic regimen has been identified. Here, we report an infant case of primary refractory GI-LCH with PLE that showed marked improvement in response to 2-chlorodeoxyadenosine (2-CdA) therapy with no severe adverse events, even under conditions of deteriorating general health. The present findings indicate that 2-CdA may be effective for refractory GI-LCH with PLE. Further studies are warranted to determine the optimal therapeutic strategies for GI-LCH with PLE.

Central diabetes insipidus in pediatric patients with Langerhans cell histiocytosis: Results from the JLSG-96/02 studies

PURPOSE

We analyzed central diabetes insipidus (CDI) development in pediatric patients with Langerhans cell histiocytosis (LCH) treated according to the Japan LCH Study Group (JLSG) regimen, which is the combination chemotherapy including cytarabine (Ara-C).

METHODS

Retrospective data from 317 patients (multisystem disease (MS), n = 206; multiple focal bone (MFB), n = 111) treated according to the JLSG-96/02 regimens were analyzed.

RESULTS

The median follow-up duration was 10.6 years (range, 0.1-21.1). A total of 50/317 (15.8%) patients developed CDI (MFB, n = 4; MS, n = 46). Of the 50 cases, CDI was already present at the time of LCH diagnosis (pre-CDI) in 25, and it newly developed after the diagnosis and initiation of treatment (post-CDI) in the other 25 cases. The cumulative incidence of post-CDI at 10-year calculated by Kaplan-Meier analysis was 9.0% for total and 12.0% for MS patients. A positive correlation with LCH lesions at the CNS risk sites at diagnosis was found in pre-CDI cases (17/164 vs 8/171; P = 0.0359), but not in post-CDI cases (14/129 vs 11/163; P = 0.254). Multivariate analysis showed that relapse at the CNS risk sites was significantly associated with post-CDI development (hazard ratio: 4.70; 95% CI, 1.29-17.1, P < 0.05).

CONCLUSIONS

In the JLSG-96/02 studies, CDI developed in 15.8% of the cohort in which half as pre- and the other half as post-CDI. Relapse, particularly at the CNS risk sites, was linked with the development of post-CDI.

Cutaneous adult xanthogranuloma with a small portion of BRAFV 600E mutated Langerhans cell histiocytosis populations: A case report and the review of published work

Histiocytoses, including Langerhans cell histiocytosis (LCH), juvenile or adult xanthogranuloma (AXG) and Rosai-Dorfman disease (RDD), are rare disorders characterized by the proliferation of cells derived from monocyte/macrophage lineages. A few cases of LCH coexisting with xanthogranuloma or RDD have been reported. The etiology of these diseases remains unclear. However, oncogenic BRAF^{V 600E} mutations have been identified in LCH. Here, we report the case of a 26-year-old Japanese man with a 3-month history of a solitary occipital nodule. No abnormality was detected in his other organs, and a total resection of the nodule was performed. Histopathological examination revealed the coexistence of LCH and AXG with prominent emperipolesis characteristic of RDD. Immunohistochemistry showed that most of the large histiocytes were positive for CD68, weakly positive or negative for S100, and negative for CD207 and CD1a, supporting the diagnosis of AXG. The tumor cells with emperipolesis did not show S100-positive findings characteristic of RDD. The focally aggregated oval histiocytic cells were positive for CD1a, CD207, CD68 and S100, and were compatible with the immunophenotype of LCH cells. In addition, these cells were positive for BRAF^{V 600E} mutation. The tumor cells in our patient exhibited a cellular morphology characteristic of multiple histiocytoses in a solitary cutaneous nodule, which may imply an etiological association among LCH, AXG and RDD. To our knowledge, this is the first report of a BRAF^{V 600E} mutation-positive case of LCH coexisting with AXG. Because patients with BRAF^{V 600E} mutation have higher risks of multisystemic LCH and recurrence, we should carefully follow up the patient.

Altered Populations of Unconventional T Cell Lineages in Patients with Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) lesions are defined by the presence of CD1a⁺/CD207⁺ myeloid cells, but many other immune cells are present including unconventional T cells, which have powerful immunoregulatory functions. Unconventional T cell lineages include mucosal-associated invariant T (MAIT) cells, type I natural killer T (NKT) cells and gamma-delta (γδ) T cells, which are associated with many inflammatory conditions, although their importance has not been studied in LCH. We characterized their phenotype and function in blood and lesions from patients with LCH, and identified a deficiency in MAIT cell frequency and abnormalities in the subset distributions of γδ T cells and NKT cells. Such abnormalities are associated with immune dysregulation in other disease settings and are therefore potentially important in LCH. Our study is the first to recognize alterations to MAIT cell proportions in patients with LCH. This finding along with other abnormalities identified amongst unconventional T cells could potentially influence the onset and progression of LCH, thereby highlighting potential targets for new immune based therapies.

A novel fusion gene PLEKHA6-NTRK3 in langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is the most common histiocytosis with constitutive activation of the RAS–RAF–MEK–ERK (MAPKinase) cell signaling pathway. We analyzed 89 cases of BRAF and MAP2K1 mutations by Sanger sequencing, of which 18 cases showed that these two gene mutations are negative. Whole genome sequencing of suitable specimens in these negative cases revealed a translocation from the 3 intron of PLEKHA6 to the 13 intron of NTRK3 in one case. We identified that this translocation could cause a novel fusion mutation, PLEKHA6‐NTRK3. Overexpression of the PLEKHA6‐NTRK3 mutant in NIH 3T3 cells enhanced MAPKinase pathway activation, promote cell growth. Our result suggested that a new mutation need be included in LCH molecular screening panel to better define its prevalence in LCH.

What's new?

Langerhans cell histiocytosis (LCH) is a rare immune and neoplastic disorder. While it is known as the most common histiocytosis with constitutive activation of the RAS‐RAF‐MEK‐ERK (MAPKinase) cell signaling pathway, its pathogenesis remains obscure. Here, whole‐genome sequencing of BRAF V600E‐negative and MAP2K1‐negative LCH cases revealed a translocation from the intron 3 of PLEKHA6 to the intron 13 of NTRK3 in one patient, identifying a novel fusion mutation. Overexpression of PLEKHA6‐NTRK3 in vitro enhanced MAPKinase pathway activation, promoting cell growth. The results support the inclusion of the fusion mutation in LCH molecular screening panel to better define its prevalence in patients.

Isolated Langerhans cell histiocytosis of the spleen: A case report

RATIONALE

Langerhans cell histiocytosis (LCH) is a relatively rare disorder characterized by the proliferation of abnormal Langerhans cells. Splenic involvement usually presents in children with multisystem LCH, and isolated LCH of the spleen is a very rare disease. Herein, we report a case of isolated splenic LCH in an adult man.

PATIENT CONCERNS

We report a case of isolated splenic LCH that first manifested with recurrent left upper abdominal pain.

DIAGNOSIS

Unenhanced CT revealed multiple nodular lesions located at the spleen. Magnetic resonance imaging speculated that these lesions were lymphomas. On the basis of histopathological and immunohistochemical findings, the diagnosis of isolated splenic LCH was confirmed.

INTERVENTION AND OUTCOMES

The patient underwent splenectomy. Histopathologic examination revealed the proliferation of Langerhans cell. Immunohistochemical staining revealed that cells of the tumor were positive for S-100, CD1a, CD45RO, and Vimentin. The patient is alive without recurrence 9 years after operation.

LESSONS

Isolated LCH of the spleen may have a favorable prognosis and splenectomy is an effective therapeutic method.

Merkel cell polyomavirus and Langerhans cell neoplasm

BACKGROUND

The relationship between various external agents such as pollen, food, and infectious agents and human sensitivity exists and is variable depending upon individual's health conditions. For example, we believe that the pathogenetic potential of the Merkel cell polyomavirus (MCPyV), the resident virus in skin, is variable and depends from the degree of individual's reactivity. MCPyV as well as Epstein-Barr virus, which are normally connected with humans under the form of subclinical infection, are thought to be involved at various degrees in several neoplastic and inflammatory diseases. In this review, we cover two types of Langerhans cell neoplasms, the Langerhans cell sarcoma (LCS) and Langerhans cell histiocytosis (LCH), represented as either neoplastic or inflammatory diseases caused by MCPyV.

METHODS

We meta-analyzed both our previous analyses, composed of quantitative PCR for MCPyV-DNA, proteomics, immunohistochemistry which construct IL-17 endocrine model and interleukin-1 (IL-1) activation loop model, and other groups' data.

RESULTS

We have shown that there were subgroups associated with the MCPyV as a causal agent in these two different neoplasms. Comparatively, LCS, distinct from the LCH, is a neoplastic lesion (or sarcoma) without presence of inflammatory granuloma frequently observed in the elderly. LCH is a proliferative disease of Langerhans-like abnormal cells which carry mutations of genes involved in the RAS/MAPK signaling pathway. We found that MCPyV may be involved in the development of LCH.

CONCLUSION

We hypothesized that a subgroup of LCS developed according the same mechanism involved in Merkel cell carcinoma pathogenesis. We proposed LCH developed from an inflammatory process that was sustained due to gene mutations. We hypothesized that MCPyV infection triggered an IL-1 activation loop that lies beneath the pathogenesis of LCH and propose a new triple-factor model.