Progress towards molecular-based management of childhood Langerhans cell histiocytosis

Targeted therapy and immunotherapy for orbital and periorbital tumors: a major review

Traditionally, for patients who are poor candidates for surgery and/or radiotherapy, palliative chemotherapy is often offered but with significant toxic side effects. However, recent advancements in our understanding of tumor biology and molecular genetics have brought new understanding to the molecular pathways of certain tumors and cancers. This has ushered in a new era of precision medicine specific to a tumor or cancer treatment pathway (targeted therapy) or directed to host-tumor responses (immunotherapy). This article will focus on recent updates in the application of available targeted and immunotherapy for managing orbital and periorbital tumors and tumor-like conditions, which include cutaneous basal cell carcinoma, cutaneous squamous cell carcinoma, cutaneous melanoma, Merkel cell carcinoma, sebaceous gland carcinoma, solitary fibrous tumor, dermatofibrosarcoma protuberans, orbital meningioma, neurofibromatosis, Langerhans cell histiocytosis, ocular adnexal lymphoma, orbital lymphatic malformation, and adenoid cystic carcinoma.

Childhood interstitial lung diseases: current understanding of the classification and imaging findings

Childhood interstitial lung diseases (chILDs) encompass a diverse group of disorders with a high mortality rate and severe respiratory morbidities. Recent investigations have revealed that the classification of adult ILDs is not valid for chILDs, particularly for ILDs of early onset. Therefore, Children's Interstitial Lung Disease Research Cooperative of North America proposed a new classification of chILDs for affected children under 2 years of age, and later another classification for affected individuals between 2 and 18 years of age. In this review, we provide an overview of the imaging findings of chILDs by classification. Most infantile ILDs have unique clinical, radiological, and molecular findings, while the manifestation of pediatric ILDs overlaps with that of adult ILDs.

Treatment of congenital Langerhans cell histiocytosis with cobimetinib

We report a case of congenital multisystem Langerhans cell histiocytosis with cutaneous and hematopoietic involvement. After the failure of first-line (vinblastine and prednisolone) and second-line (vincristine and cytarabine) therapies, treatment with cobimetinib, a mitogen-activated protein kinase (MEK) inhibitor, led to the remission of disease and a sustained response after 11 months of ongoing treatment. Protein kinase inhibitors targeting BRAF or MEK could represent a promising future therapeutic option, also in children with LCH.

Solitary Langerhans cell histiocytosis of the sternum in a 21-year-old woman

Children are more likely to develop Langerhans cell histiocytosis (LCH), a rare disorder with an unknown cause. LCH often invades skeletal systems, while it has occasionally been seen in the sternum or ribs. The best course of treatment for single-site, skeletal LCH is yet unknown. We present an instance of sternal LCH with adult onset. By fusing and reconstructing chest computed tomography, it was possible to determine the extent of surrounding soft tissue invasion. Because LCH is so uncommon, it could be challenging to recall when we see a sternal lesion. Adult Patients who arrive with anterior chest discomfort and an osteolytic sternal lesion should include LCH on their differential diagnosis list.

[Therapeutic Strategies In Children And Adolescents With Langerhans Cell Histiocytosis]

The current standard therapy for children and adolescents with newly diagnosed Langerhans cell histiocytosis (LCH) is based on the two drugs prednisone and vinblastine. In patients with insufficient treatment response or disease relapse, the choice of second-line treatment depends on risk organ involvement (liver, spleen, and hematopoietic system). This article will give an overview of current data concerning therapeutic options in the different settings of children and adolescents with LCH. Due to limited evidence, these strategies have not been described in detail in the updated guidelines on pediatric LCH. In addition, the use of targeted therapy such as MAP-kinase inhibitors will be discussed. The reference center for LCH should be contacted if therapeutic options beyond the standard regimen are considered for treatment. All children and adolescents with LCH should be enrolled in registries or prospective studies.

Novel therapeutic approaches for pediatric diencephalic tumors: improving functional outcomes

Pediatric diencephalic tumors represent a histopathologically and molecularly diverse group of neoplasms arising in the central part of the brain and involving eloquent structures, including the hypothalamic-pituitary axis (HPA), optic pathway, thalamus, and pineal gland. Presenting symptoms can include significant neurological, endocrine, or visual manifestations which may be exacerbated by injudicious intervention. Upfront multidisciplinary assessment and coordinated management is crucial from the outset to ensure best short- and long-term functional outcomes. In this review we discuss the clinical and pathological features of the neoplastic entities arising in this location, and their management. We emphasize a clear move towards 'function preserving' diagnostic and therapeutic approaches with novel toxicity-sparing strategies, including targeted therapies.

Clinical outcomes and prognostic risk factors of Langerhans cell histiocytosis in children: Results from the BCH-LCH 2014 protocol study

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm mainly affecting young children. This study aimed to evaluate the outcomes of 449 pediatric patients enrolled in the BCH-LCH 2014 study. 52.6% of patients were classified with single-system (SS) LCH, 28.1% with multisystem (MS) risk organ negative (RO-) LCH, and 19.4% with MS RO+ LCH. Three hundred ninety-six patients (88.2%) were initially treated with first-line therapy based on the vindesine-prednisone combination. One hundred thirty-nine patients who lacked a response to initial treatment were shifted to second-line therapy, 72 to intensive treatment Arm S1 (a combination of cytarabine, cladribine, vindesine, and dexamethasone), and 67 to Arm S2 (without cladribine). The 5-year overall survival (OS), progression-free survival (PFS), and relapse rates were 98.2% (median: 97.6 months), 54.6% (median: 58.3 months), and 29.9%, respectively. MS RO+ patients had the worst prognosis among the three clinical subtypes. For the patients initially treated with first-line therapy, the 5-year OS, PFS, and relapse rates were 99.2%, 54.5%, and 29.3%, respectively. Patients in Arm S1 had a significantly better prognosis than patients in Arm S2 (5-year PFS: 69.2% vs. 46.5%, p = .042; relapse rate: 23.4% vs. 44.2%, p = .031). Multivariate analysis revealed that early treatment response, the involvement of RO, skin, and oral mucosa, as well as laboratory parameters, including CRP and γ-GT, were independent risk factors for the PFS of LCH. Thus, the prognosis of LCH in children has been improved significantly with stratified chemotherapy, and progression and relapse remained the challenges, especially for RO+ patients.

Langerhans cell histiocytosis. Advances in pathogenesis and clinical practice

Langerhans cell histiocytosis (LCH) is a type of myeloid neoplasia that can affect different organs or tissues and exhibits substantial variability in its clinical presentation and biological behaviour, so it may mimic different diseases. Performance of different clinical assessments and laboratory and imaging tests is recommended to determine the extent of involvement, which may be of a single location or multisystemic, and the presence or absence of dysfunction in risk organs, such as the haematopoietic system, liver and spleen. The diagnosis must be confirmed by histological examination of a biopsy sample. Molecular tests have identified mutations in the mitogen-activated protein kinase (MAPK) pathway, which has expanded treatment options. The diagnosis is complex and there is controversy regarding the management of certain cases. Treatment recommendations depend on the location of the lesions and the extent of involvement. International collaborative studies have demonstrated the effectiveness of prolonged combination therapies such as vinblastine and prednisone in severe or multisystemic forms, and anti-inflammatory drugs such as indomethacin and other cytostatic combinations have proven beneficial. Langerhans cell histiocytosis is a good example of the importance of precision medicine and the benefit of identifying molecular targets, common to different neoplasms, to develop new therapies. MAPK pathway inhibitors offer an alternative treatment option in refractory cases and neurodegenerative forms of LCH. Molecular testing can contribute to the prognosis, treatment and follow-up of LCH, especially in severe forms of disease.

Monitoring Circulating CD207+CD1a+ Cells in Langerhans Cell Histiocytosis and Clinical Implications

Langerhans cell histiocytosis (LCH) is a disorder characterized by an abnormal accumulation of CD207⁺ and CD1a⁺ cells in almost any tissue. Currently, there is a lack of prognostic markers to follow up patients and track disease reactivation or treatment response. Putative myeloid precursors CD207⁺ and CD1a⁺ cells were previously identified circulating in the blood. Therefore, we aim to develop a sensitive tracing method to monitor circulating CD207⁺ and CD1a⁺ cells in a drop of blood sample of patients with LCH. A total of 202 blood samples from patients with LCH and 23 controls were tested using flow cytometry. A standardized cellular score was defined by quantifying CD207⁺ and CD1a⁺ expression in monocytes and dendritic cells, based on CD11b, CD14, CD11c, and CD1c subpopulations, resulting in a unique value for each sample. The scoring system was validated by a receiver operating characteristic curve showing a reliable discriminatory capacity (area under the curve of 0.849) with a threshold value of 14, defining the presence of circulating CD207⁺ and CD1a⁺ cells. Interestingly, a fraction of patients with no evident clinical manifestation at the time of sampling also showed presence of these cells (29.6%). We also found a differential expression of CD207 and CD1a depending on the organ involvement, and a positive correlation between the cellular score and plasma inflammatory markers such as soluble CD40L, soluble IL-2Ra, and CXCL12. In conclusion, the analysis of circulating CD207 and CD1a cells in a small blood sample will allow setting a cellular score with minimal invasiveness, helping with prognostic accuracy, detecting early reactivation, and follow-up.

Neutralizing Anti-IL-17A Antibody Demonstrates Preclinical Activity Enhanced by Vinblastine in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm characterised by the accumulation into granulomas of apoptosis-resistant pathological dendritic cells (LCH-DCs). LCH outcome ranges from self-resolving to fatal. Having previously shown that, (i) monocyte-derived DCs (Mo-DCs) from LCH patients differentiate into abnormal and pro-inflammatory IL-17A-producing DCs, and (ii) recombinant IL-17A induces survival and chemoresistance of healthy Mo-DCs, we investigated the link between IL-17A and resistance to apoptosis of LCH-DCs. In LCH granulomas, we uncovered the strong expression of BCL2A1 (alias BFL1), an anti-apoptotic BCL2 family member. In vitro, intracellular IL-17A expression was correlated with BCL2A1 expression and survival of Mo-DCs from LCH patients. Based on the chemotherapeutic drugs routinely used as first or second line LCH therapy, we treated these cells with vinblastine, or cytarabine and cladribine. Our preclinical results indicate that high doses of these drugs decreased the expression of Mcl-1, the main anti-apoptotic BCL2 family member for myeloid cells, and killed Mo-DCs from LCH patients ex vivo, without affecting BCL2A1 expression. Conversely, neutralizing anti-IL-17A antibodies decreased BCL2A1 expression, the downregulation of which lowered the survival rate of Mo-DCs from LCH patients. Interestingly, the in vitro combination of low-dose vinblastine with neutralizing anti-IL-17A antibodies killed Mo-DCs from LCH patients. In conclusion, we show that BCL2A1 expression induced by IL-17A links the inflammatory environment to the unusual pro-survival gene activation in LCH-DCs. Finally, these preclinical data support that targeting both Mcl-1 and BCL2A1 with low-dose vinblastine and anti-IL-17A biotherapy may represent a synergistic combination for managing recurrent or severe forms of LCH.

Liver transplantation in a child with liver cirrhosis caused by langerhans cell histiocytosis: a case report

Background

Langerhans cell histiocytosis (LCH) is a rare condition that has a variety of clinical manifestations. But LCH in children localized only in the hepatobiliary system is unusual.

Case presentation.

Here we reported a rare case of a 2-year-old boy who was serendipitously found to have elevated liver enzymes while undergoing treatment of a perianal abscess. After a period of earlier conservative treatment in another hospital, the perianal abscess had resolved but the levels of liver enzymes were still rising slowly. The child was then referred to our institution for a definitive diagnosis. After laboratory tests, imaging and pathological examinations, a diagnosis of liver cirrhosis and sclerosing cholangitis was established, although the cause was unclear. Subsequently, living-donor liver transplantation was performed due to deterioration in liver function. Following successful liver transplantation, a diagnosis of LCH localized only within the hepatobiliary system was finally confirmed, based on additional pathological and imaging investigation. Additionally, the BRAF V600E mutation in this patient was also confirmed. The child has now recovered without evidence of LCH recurrence.

Conclusions

LCH localized only within the hepatobiliary system is unusual. The presence of unexplainable sclerosing cholangitis and liver cirrhosis in any child should raise the suspicion of LCH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-03090-4.

Current diagnosis and management of rare pediatric diseases in China

This review categorizes and summarizes the rare pediatric diseases that have been included in the First List of Rare Diseases that was jointly published by the National Health Commission and four other government departments in China in 2018. In total, 58 diseases that develop during childhood are included. These diseases involve nine organ systems, including the musculoskeletal, respiratory, immune, endocrine and metabolic, nervous, cardiovascular, hematological, urinary, and integumentary systems. Affected children often have multiorgan involvement with various presentations. Severe diseases can cause acute symptoms starting in the neonatal period that lead to increased morbidity and mortality without prompt management. Early diagnosis and treatment can significantly change the course of a disease and improve its prognosis. This work systemically reviews the status of rare pediatric diseases with a relatively high incidence in the First List of Rare Diseases.

Mitogen-activating protein kinase pathway alterations in Langerhans cell histiocytosis

PURPOSE OF REVIEW

Langerhans cell histiocytosis (LCH) is a rare disorder characterized by the infiltration of involved tissues by specialized dendritic cells. The demonstration of the constant activation of the mitogen-activated protein kinase (MAPK) pathway in LCH lesions has been a breakthrough in the understanding of the pathogenesis of this rare disease. We will summarize the current knowledge on MAPK alterations in LCH and the new therapeutic options indicated by these findings.

RECENT FINDINGS

Since the description of the B-Raf proto-oncogene, serine/threonine kinase (BRAF)V600E mutation in LCH lesions, several other molecular alterations affecting the MAPK pathway have been identified in most cases. Based on these driver alterations, LCH cells were shown to be derived from hematopoietic precursors, which yielded the current concept of LCH as a myeloid inflammatory neoplasia. MAPK pathway inhibitors have emerged as an innovative therapy in severe forms of LCH, resulting in virtually no acquired resistance. However, although they are highly effective, their effect is only temporary, as the disease relapses upon discontinuation of the treatment.

SUMMARY

LCH is an inflammatory myeloid neoplastic disorder, driven by mutations activating the MAPK pathway. MAPK-targeted treatments represent an important stepforward in the management of patients with severe progressive LCH.

Transcriptomic Landscape of Circulating Mononuclear Phagocytes in Langerhans Cell Histiocytosis at Single-cell Level

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm caused by aberrant activation of the mitogen-activated protein kinase (MAPK) pathway. Circulating myeloid cells from patients often carry disease-associated mutations and can be differentiated into langerinhigh LCH-like cells in vitro, but their detailed immune-phenotypic and molecular profiles are lacking and could shed key insights into disease biology. Here we recruited 217 pediatric LCH patients and took blood and tissue samples for BRAFV600E analysis. Immune-phenotyping of the circulating Lin-HLA-DR+ immune population in 49 of these patients revealed that decreased frequency of pDC was significantly linked to disease severity. By single-cell RNA sequencing of samples from 14 patients, we identified key changes in expression of RAS-MAPK-ERK signaling-related genes and transcription factors in distinct members of the mononuclear phagocyte system in the presence of BRAFV600E. Moreover, treatment of patients with the BRAF inhibitor Dabrafenib resulted in MAPK cascade inhibition, inflammation prevention, and regulation of cellular metabolism within mononuclear phagocytes. Finally, we also observed elevated expression of RAS-MAPK-ERK signaling-related genes in a CD207+CD1a+ cell subcluster in skin. Taken together, our data extends the molecular understanding of LCH biology at single-cell resolution, which might contribute to improvement of clinical diagnostics and therapeutics, and aid in the development of personalized medicine approaches.

Recent advances in the understanding of the molecular pathogenesis and targeted therapy options in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is the most common histiocytic disorder caused by the clonal expansion of myeloid precursors that differentiate into CD1a+/CD207+ cells in the lesion. Advances in genomic sequencing techniques have improved our understanding of the pathophysiology of LCH. Activation of the mitogen-activated protein kinase (MAPK) pathway is a key molecular mechanism involved in the development of LCH. Recurrent BRAF mutations and MAP2K1 mutations are the major molecular alterations involved in the activation of the MAPK pathway. Recent studies have supported the “misguided myeloid differentiation model” of LCH, where the extent of disease is defined by the differentiation stage of the cell in which the activating somatic MAPK mutation occurs, suggesting LCH. Several studies have advocated the efficacy of targeted therapy using BRAF inhibitors with a high response rate, especially in patients with high-risk or refractory LCH. However, the optimal treatment scheme for children remains unclear. This review outlines recent advances in LCH, focusing on understanding the molecular pathophysiology, emerging targeted therapy options, and their clinical implications.

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

BACKGROUND

Lung involvement in childhood Langerhans cell histiocytosis (LCH) is infrequent and rarely life threatening, but occasionally, severe presentations are observed.

METHODS

Among 1482 children (< 15 years) registered in the French LCH registry (1994-2018), 111 (7.4%) had lung involvement. This retrospective study included data for 17 (1.1%) patients that required one or more intensive care unit (ICU) admissions for respiratory failure.

RESULTS

The median age was 1.3 years at the first ICU hospitalization. Of the 17 patients, 14 presented with lung involvement at the LCH diagnosis, and 7 patients (41%) had concomitant involvement of risk-organ (hematologic, spleen, or liver). Thirty-five ICU hospitalizations were analysed. Among these, 22 (63%) were secondary to a pneumothorax, 5 (14%) were associated with important cystic lesions without pneumothorax, and 8 (23%) included a diffuse micronodular lung infiltration in the context of multisystem disease. First-line vinblastine-corticosteroid combination therapy was administered to 16 patients; 12 patients required a second-line therapy (cladribine: n = 7; etoposide-aracytine: n = 3; targeted therapy n = 2). A total of 6 children (35%) died (repeated pneumothorax: n = 3; diffuse micronodular lung infiltration in the context of multisystem disease: n = 2; following lung transplantation: n = 1). For survivors, the median follow-up after ICU was 11.2 years. Among these, 9 patients remain asymptomatic despite abnormal chest imaging.

CONCLUSIONS

Severe lung involvement is unusual in childhood LCH, but it is associated with high mortality. Treatment guidelines should be improved for this group of patients: viral infection prophylaxis and early administration of a new LCH therapy, such as targeted therapy.