Mitogen-activating protein kinase pathway alterations in Langerhans cell histiocytosis

[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.

Pediatric diencephalic tumors: a constellation of entities and management modalities

The diencephalon is a complex midline structure consisting of the hypothalamus, neurohypophysis, subthalamus, thalamus, epithalamus, and pineal body. Tumors arising from each of these diencephalic components differ significantly in terms of biology and prognosis. The aim of this comprehensive review is to describe the epidemiology, clinical symptoms, imaging, histology, and molecular markers in the context of the 2021 WHO classification of central nervous system neoplasms. We will also discuss the current management of each of these tumors.

Langerhans Cell Histiocytosis: A Population-based Study of Anatomical Distribution and Treatment Patterns

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LCH in bone marrow and lymph node are more likely to have multi-system involvement compared to LHC in other sites.

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Craniofacial osseous LCH is more likely to be treated with surgery, vertebral LCH is less likely to be treated with surgery.

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A racial disparity in surgery utilization is identified in pediatric patients with bone LCH.

Background

Langerhans cell histiocytosis (LCH) is a rare monoclonal histiocytic neoplasm. Little is known about clinical factors associated with LCH single- vs multi-system involvement at the time of diagnosis.

Methods

Data on 1549 LCH patients diagnosed between years 2010 and 2018 were extracted from the Surveillance, Epidemiology and End Results Program. Patterns of single- vs multisystem involvement were examined using multivariable logistic regression analysis. Odd ratio (OR) and 95% confidence interval (CI) were reported.

Results

968 children and adolescents (0–19 years; median: 4 years) and 581 adults (≥20 years; median: 49 years) were included in the analysis. Multi-system LCH was reported for 30.9 % patients. Bone marrow (BM) (OR = 3.776; 95 %CI = 1.939–7.351; P < 0.001) and lymph node (LN) (OR = 3.274; 95 %CI = 1.443–7.427; P = 0.005) involvement were most commonly associated with multi-system LCH at the time of diagnosis; similar pattern was also observed in adult patients (OR = 17.780; 95 %CI = 6.469–48.867; P < 0.001 for BM LCH; and OR = 5.156; 95 %CI = 2.131–12.471; P < 0.001 for LN LCH). Among pediatric patients, craniofacial osseous LCH was more likely to be treated with surgery (OR = 2.822; 95 %CI = 1.199–6.639; P = 0.018) compared to skeletal lesions in other sites, whereas vertebral body LCH was less likely to be treated with surgery (OR = 0.175; 95 %CI = 0.058–0.527; P = 0.002). In pediatric patients with bone LCH, the non-white patients were less likely to be treated surgically compared to the white patients (OR = 0.470; 95 %CI = 0.272–0.812; P = 0.007).

Conclusions

BM and LN LCH are associated with the highest risks of multi-system disease, which may require active surveillance. Furthermore, active attempts are needed to mitigate the racial disparity in surgery utilization in pediatric patients with skeletal LCH.

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.