Langerhans Cell Histiocytosis Lesions Research Articles

Genetic Landscape and Its Prognostic Impact in Children With Langerhans Cell Histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm that predominantly affects young children. To investigate genetic alterations and their correlation with clinical characteristics and prognosis in pediatric LCH. We performed targeted sequencing to detect mutations in LCH lesions from pediatric patients. A total of 30 genomic alterations in 5 genes of the MAPK pathway were identified in 187 of 223 patients (83.9%). BRAF V600E (B-Raf proto-oncogene, serine/threonine kinase) was the most common mutation (51.6%), followed by MAP2K1 (mitogen-activated protein kinase kinase 1) alterations (17.0%) and other BRAF mutations (13.0%). ARAF (A-Raf proto-oncogene, serine/threonine kinase) and KRAS (KRAS proto-oncogene, GTPase) mutations were relatively rare (2.2% and 0.9%, respectively). Additionally, FNBP1 (formin-binding protein 1)::BRAF fusion and MAP3K10 (mitogen-activated protein kinase kinase 10) mutations A17T and R823C were identified in 1 case each, with possible constitutive activation of ERK1/2 phosphorylation. BRAF V600E was more frequent in patients with risk organ involvement, while MAP2K1 mutation was more prevalent in patients with single-system LCH (P = .001). BRAF V600E was associated with craniofacial bone, skin, liver, spleen, and ear involvement (all P < .05). Patients with other BRAF mutations had a higher proportion of spinal column involvement (P = .006). Univariate analysis showed a significant difference in progression-free survival among the 4 molecular subgroups for patients treated with first-line therapy (P = .02). According to multivariate analysis, risk organ involvement was the strongest independent adverse prognostic factor (hazard ratio, 8.854; P < .001); BRAF or MAP2K1 mutation was not an independent prognostic factor. Most pediatric patients with LCH carry somatic mutations involving the MAPK pathway, correlating with clinical characteristics and outcomes for first-line chemotherapy.

The value of 18F-FDG PET/CT in Langerhans cell histiocytosis.

To investigate the value of 18F-FDG PET/CT in diagnosis and disease evaluation of Langerhans cell histiocytosis (LCH). A retrospective analysis of 31 patients with LCH confirmed by histopathology was performed. A systematic analysis of the PET/CT imaging manifestations of LCH was performed, recording patients who were treated and receiving PET/CT for efficacy evaluation. In addition, clinical and laboratory data of LCH patients were collected, and the correlation between these data and PET/CT metabolic parameters was initially investigated. Of the 31 patients, thirty had at least 1 PET/CT positive lesions (96.7%), and one had only skin damage without abnormalities on PET/CT. Of 31 patients, fifteen (48.4%) had single system (SS) disease (9 cases with a single site and 6 cases with multiple sites) and 16 (51.6%) had multisystem (MS) disease (6 low risk and 10 high risk cases). The incidence of LCH lesions in the bone, lymphatic system, pituitary gland, liver, soft tissue, thyroid gland, thymus, and lungs was 20 cases (64.5%), 12 cases (38.7%), 3 cases (9.7%), 2 cases (6.5%), 2 cases (6.5%), 1 case (3.2%), 1 case (3.2%), and 8 cases (25.8%), respectively. A total of 21 PET/CT follow-up scanning were performed in 13 patients receiving chemotherapy, with 13 (61.9%) partial metabolic remission (PMR), 6 (28.6%) progressive metabolic disease (PMD), and 2 (9.5%) stable metabolic disease (SMD), according to PET Response Evaluation Criteria in Solid Tumors (PRECIST) 1.0. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and Lactic Dehydrogenase (LDH) were positively correlated with TTLG (total TLG) (R2 = 0.3256, 0.2409, 0.4205, P < 0.05). The Re-examine SUVmax is positively correlated with re-examine LDH (R2 = 0.7285, P < 0.05). 18F-FDG PET/CT is an effective way to diagnose and evaluate LCH. PET metabolic parameters were associated with laboratory inflammatory markers, suggesting that 18F-FDG PET/CT may be helpful in evaluating disease activity of LCH.

Abstract B073: Leveraging genomic diversity identifies additional germline risk loci in SMAD6 for Langerhans cell histiocytosis

Abstract Background: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by lesions including pathogenic CD207+ dendritic cells among an inflammatory infiltrate with recurrent, mutually exclusive somatic activating mutations in MAPK pathway genes in ~85% of LCH lesions; however, germline risk factors remain largely unknown. A SEER analysis reported that incidence of high-risk LCH was higher in Hispanic populations than non-Hispanic populations, and lowest in non-Hispanic Black populations. Our group reported that Hispanic mothers/couples were more likely to have children with LCH compared to non-Hispanic white mothers/couples. In the first GWAS of LCH, our group identified and validated a risk variant in SMAD6 associated with a 3-fold increase in risk. Our current objective is to leverage the genomic diversity of our patient population to identify additional SMAD6 LCH risk loci. Methods: Cases diagnosed with LCH were recruited at Texas Children’s Hospital (n=466). Targeted sequencing of SMAD6 was conducted among cases with ~200x coverage at the Avera Institute of Human Genetics. We accessed aggregate-level SMAD6 sequence data in SMAD6 from a median of 15,694 non-cancer controls in gnomAD v2.1.1. Fisher’s exact test was applied to 154 SMAD6 variants (Bonferroni critical P-value of 3.2 x 10-4) to assess association between SMAD6 variation and case status. Analyses were conducted with SAS and population genetics were assessed in Ensembl. Results: In this case-control analysis, 49 variants were significantly associated with LCH risk, including our previous risk locus. Leveraging population genetics, we found that the top 4 SNPs have low MAF globally (range 2-9%) but are enriched (MAF range 15-23%) in Hispanic/Latinx populations (MXL, CLM, PEL). The top two hits are in high LD in some of the Hispanic/Latinx and Black (ASW) populations (r2: MXL= 0.71, ASW = 1.0, PEL = 0.92), but not globally. The third SNP is in high LD with the peak SNP in these populations, as well (r2: MXL= 0.28, ASW = 0.83, PEL = 0.51). The fourth hit, which is our previously identified risk locus, has moderate LD with the peak SNP in Hispanic/Latinx populations (r2: MXL= 0.31, CLM = 0.3, PEL = 0.13). Conversely, the LD between the 1st and 5th SNPs was low globally and within different populations. Conclusion: We identified additional support for the role of SMAD6 variation in LCH susceptibility across and within diverse ancestral populations. These findings suggest that the top four SMAD6 variants identified in this study vary in how they function as independent signals across populations, especially in Hispanic/Latinx patients. The 5th hit in SMAD6 appears to be the next independent variant across all populations. These results indicate that there are common risk variants across populations and ancestry-specific variants for LCH, which may contribute to the differences in ancestry-specific LCH risk. Broadly, our work emphasizes the benefits of leveraging in, rather than adjusting out, the genomic richness of diverse patient populations. Citation Format: Priya B. Shetty, Erin Peckham-Gregory, Erik Stricker, Howard Lin, Brooks Scull, Erik Ehli, Christel Davis, Kenneth McClain, Philip Lupo, Carl Allen, Michael Scheurer. Leveraging genomic diversity identifies additional germline risk loci in SMAD6 for Langerhans cell histiocytosis [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr B073.

First Blood: Pre-Therapy BRAFV600E+ PBMC Identifies a Novel Clinical Risk Category for Patients with LCH

Purpose: Langerhans Cell Histiocytosis (LCH) is a myeloproliferative neoplasia driven by somatic mutations in the mitogen-activated protein kinases pathway (MAPK). LCH has historically been clinically staged as “high risk” (e.g. liver, spleen and/or bone marrow involvement, HR) or “low risk” (LR) due relative to risk of death in earlier trials. However, clinical staging is complicated by different sensitivities of imaging and, more recently, molecular analyses. We previously identified that BRAFV600E allele in peripheral blood mononuclear cells (PBMC) in patients with HR LCH, which supported a model of LCH arising from hematopoietic myeloid precursors. To determine the clinical significance of somatic lesion BRAFV600E mutations as well as ability to detect pre-therapy BRAFV600E+ PBMC at diagnosis, we analyzed an extended cohort of LCH patients with longitudinal clinical evaluations. Methods: Genomic DNA was isolated from 366 lesion biopsies and the PBMCs of 294 patients with active LCH before initial therapy. The percentage of PBMC with the BRAFV600E allele in patients was determined by quantitative polymerase chain reaction. Lesion genotype and ability to detect pre-therapy BRAFV600E in PBMC were correlated with clinical features including i) clinical risk status, ii) extent of disease (single lesion vs multifocal; single system vs multisystem), iii) response to therapy, v) and time to relapse were analyzed using a chi-square test. Fluorescence-activated cell sorting (FACS), DNA amplification and subsequent qPCR was performed on 15 pretherapy BRAFV600E+ blood samples to explore the relationship between different myeloid lineages (CD3, CD19, CD56, CD14, CD16, CD11c) and extent of LCH disease. Survival proportions were calculated using the Kaplan-Meier (product limit) method and a log-rank (Mantel-Cox) test was used to calculate the significance of the difference between survival curves. Results: Median age was 3.01 years (range 3.6 days to 21.5 years), 58.5% of the patients were male (41.5% female), and 15.4% had HR disease (84.6% LR). Among patients with LR disease, 33.0% had multisystem, 23.1% had multi-focal single system, and 44.0% had single lesions. Lesion genotypes were 51.9% BRAFV600E and 49.1% not BRAFV600E. BRAFV600E in LCH lesions was associated with lower age at diagnosis and higher prevalence of HR disease. However, after a median follow-up time of 1.6 years (range 1 month to 8.5 years) there was no difference in EFS between BRAFV600E and alternative mutations (p=0.35). Notably, for the entire cohort, presence of BRAFV600E in diagnostic PBMC was highly associated with younger patients, clinical HR disease and risk of developing LCH-associated neurodegeneration (LCH-ND). For patients with BRAFV600E+ lesions, 32.5% had detectable BRAF V600E in pre-therapy PBMC: 100% of HR, 52.6% of multisystem LR, 18.4% of multi-focal single system LR and 0% of single lesion. Further, after a median follow-up time of 2.0 years (range 1 month to 9,1 years) clinical LR PBMC BRAFV600E+ represented a group at higher risk of treatment failure compared to BRAFV600E-neg LR (p=0.01). BRAFV600E alleles were present in PBMC at diagnosis in all of the sorted myeloid populations, with consistent enrichment in myeloid dendritic cells and monocytes. There was no significant correlation between BRAFV600E allele burden (percentage of BRAFV600E+ PBMC) and clinical risk, and no significant differences in the distribution of allele burden within lineages. Conclusion: Ability to detect pretherapy BRAFV600E+ represents an important clinical biomarker for patients with LCH. Results from this study support the potential for pre-therapy PBMC BRAFV600E to predict clinical risks, inform pathogenic mechanisms in LCH, and identify LR PBMC BRAFV600E+ as a novel clinical risk group. We hypothesize that persistence of hematopoietic clones and circulating myeloid precursors may underlie the increased risks of treatment failure and development of LCH-ND in patients previously presumed to have “low risk” disease.

Identification of Germline, Ancestry-Specific Variants for Langerhans Cell Histiocytosis in Hispanic Patients

Background: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by lesions including pathogenic CD207+ dendritic cells among an inflammatory infiltrate with recurrent, mutually exclusive somatic activating mutations in MAPK pathway genes in ~85% of LCH lesions. Our group and others have reported that Hispanic populations are more likely to develop LCH, particularly high-risk LCH, than non-Hispanic counterparts. Our group previously identified and validated a risk SNP in SMAD6 associated with a 3-fold increase in LCH risk that was also enriched in those of Hispanic ancestry; however, germline risk factors have yet to be fully elucidated in the higher-risk Hispanic population. Methods: Using targeted SMAD6 sequence data from 466 cases with LCH and aggregate data for 15,694 non-cancer controls from gnomAD v2.1.1, we evaluated 49 SNPs previously associated with case status to identify those that were enriched specifically in Hispanic populations. We conducted an additional genome-wide association study (GWAS) on 98 LCH cases and 1,158 controls, all inferred to be Hispanic based on global genomic ancestry. The GWAS was adjusted for the first 3 PCs. Population genetics were assessed in Ensembl, ancestry inference was conducted Admixture software (reference panel 1000 Genomes, Phase 3), and statistical analyses were conducted with PLINK, Stata, and SAS software. Results: In the population genetics analysis of the SMAD6 SNPs, the top 4 SNPs (Figure 1) have a lower minor allele frequency (MAF) of 2-9% across all populations. However, in Hispanic populations, the alternate/risk allele in the top 4 SNPs is increased (MAF range 15-23%). Furthermore, the LD between the top four SNPs is enriched among Hispanic populations (range of r 2: 0.51-0.92; Table 1), suggesting that Hispanic patients may have different risk loci compared to others. In the LCH GWAS of Hispanic patients, there were no statistically significant SNPs; however, this pilot study of our ongoing analyses identified 5 LCH risk loci in Hispanic patients that had suggestive significant associations ( P=1.0x10 -5). Strikingly, these loci differed from the SNPs identified in our GWAS of all patients. Conclusions: Using multiple approaches, we have identified LCH risk variants that were identified in Hispanic patients. These Hispanic ancestry-specific risk SNPs were more strongly associated with case status in Hispanic patients than the risk SNPs from our GWAS of all patients. This indicates that the ancestry-specific SNPs may contribute to the increased risk of LCH, particularly high-risk LCH, that is seen in Hispanic populations compared to populations of other ancestries. Our ongoing work involves assessing these SNPs for association with patient and clinical characteristics and outcomes in Hispanic patients. In addition, we are determining how these Hispanic ancestry-specific variants affect risk of LCH in patients of other ancestries, identifying additional ancestry-specific risk SNPs in patients of other ancestries, and examining the effects of global and ancestry-specific risk SNPs on LCH risk.

Expanded Assessments of Germline Genetic Variants Identify Additional Risk Loci for Langerhans Cell Histiocytosis

Introduction: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by lesions including pathogenic CD207+ dendritic cells among an inflammatory infiltrate. Sequencing studies have identified recurrent, mutually exclusive somatic activating mutations in MAPK pathway genes in ~85% of LCH lesions, including BRAF V600E in 50-65%. Despite advances to elucidate the somatic mutational landscape underlying LCH pathogenesis, germline risk factors remain largely unknown. We previously conducted the first genome-wide association study (GWAS) of LCH and identified and validated a risk variant in SMAD6 (rs12438941, G-&amp;gt;A) associated with a 3-fold increase in LCH risk. Our current objective is to further elucidate the role of SMAD6 variation on LCH risk and identify novel LCH susceptibility loci. Methods: Independent of our discovery GWAS, we sequenced SMAD6 in 466 additional LCH cases and compared them to aggregate-level SMAD6 data from ~15,694 non-cancer controls in gnomAD v2.1.1. Targeted sequencing of SMAD6 was conducted among these cases with ~200x coverage at the Avera Institute of Human Genetics. In parallel, we conducted a GWAS of 319 of those cases and leveraged controlled-access data from 9,921 controls in the ADDHealth study. Genotyping of the 319 cases was also performed at the Avera Institute for Human Genetics on the Illumina Infinium Global Screening Array. We evaluated the role of common variants (minor allele frequency &amp;gt;5%) on LCH risk and applied principal components analysis to account for potential population stratification. A genome-wide threshold of significance was applied at P-value&amp;lt;5.0x10 -8, and threshold of suggestive significance at P-value&amp;lt;1.0x10 -6. Analyses were conducted in Plink and STATAv17.1. Results: The case-control study of targeted SMAD6 identified novel SMAD6 variants associated with LCH risk ( P-values ranging from 4.54x10 -28 to 2.9x10 -4), including our original GWAS locus. All cases with two copies of the alternate alleles in the top 2 SNPs had BRAF V600E + lesions. In terms of the new GWAS, 31 novel loci were associated with LCH at P-value=5x10 -8, including 2 separate loci on Chr 9, with the top hit being intergenic between KCNV2 and VLDLR on Chr 9 and the second being intergenic between OLFM1 and LOC401557. Other identified top hits suggest putative biologic significance in terms of LCH pathogenesis. Conclusion: We identified additional support that inherited genetic variation impacts LCH risk. We are concurrently assessing the role of ancestry-specific loci on LCH risk and analyzing newly generated SMAD6 targeted sequence and GWAS data in an independent set of case-parent trios (n=185) to integrate with the findings reported here. Next steps include a meta-analysis of our discovery GWAS, the new GWAS reported here, and the recently genotyped new set of 185 case-parent trios. We also aim to determine the role of variants on clinical characteristics (e.g., ancestry, age at onset, BRAF V600E). Our work suggests an important and complex role of germline variants and ancestry in LCH pathogenesis.

Presentation, treatment, and outcomes of unifocal and multifocal osseous vertebral Langerhans cell histiocytosis lesions in patients under 18 years old.

This study aims to (1) clinically and radiographically characterize a series of unifocal (single-system single-site) and multifocal (single-system multiple-site) langerhans cell histiocytosis (LCH) lesions in the vertebra and (2) determine the success and recurrence rates with different treatment modalities in a pediatric population at a tertiary children's hospital. Patients younger than 18 years old with a diagnosis of LCH before 1 June 2021 at our institution were reviewed. The inclusion criteria were a unifocal or multifocal vertebral lesion without systemic disease. Clinical presentations, lesion sites, radiographic findings, treatments, complications, recurrence rates, and length of follow-up were reviewed and recorded. Thirty-nine patients had unifocal (36%) or multifocal (64%) vertebral lesions. 44% of patients had vertebral lesions only. The most common clinical presentation was neck or back pain (51%) and difficulty or inability to ambulate (15%). 70 vertebrae were involved in total; 59% cervical, 62% thoracic, 49% lumbar, and 10% sacral. 88% of multifocal patients underwent chemotherapy compared to 60% of unifocal patients. The recurrence rate in the entire cohort was 10%. The median length of follow-up was 5.2 years (0.6-16.8). Chemotherapy is often utilized as a treatment for vertebral LCH lesions regardless of unifocal or multifocal osseous presentation, with good outcomes and low recurrence rates. However other treatments such as observation only and steroid injections may be a better option with smaller and less widespread lesions due to side effects and length of treatment with chemotherapy. Determination of more invasive treatments including surgical excision or fixation will need to be considered on a case-by-case basis. Level of evidence: IV.

Multiple Langerhans cell histiocytosis with spinal involvement.

The aim of this study was to report the long-term prognosis of patients with multiple Langerhans cell histiocytosis (LCH) involving the spine, and to analyze the risk factors for progression-free survival (PFS). We included 28 patients with multiple LCH involving the spine treated between January 2009 and August 2021. Kaplan-Meier methods were applied to estimate overall survival (OS) and PFS. Univariate Cox regression analysis was used to identify variables associated with PFS. Patients with multiple LCH involving the spine accounted for 15.4% (28/182 cases) of all cases of spinal LCH: their lesions primarily involved the thoracic and lumbar spines. The most common symptom was pain, followed by neurological dysfunction. All patients presented with osteolytic bone destruction, and 23 cases were accompanied by a paravertebral soft-tissue mass. The incidence of vertebra plana was low, whereas the oversleeve-like sign was a more common finding. The alkaline phosphatase was significantly higher in patients with single-system multifocal bone LCH than in patients with multisystem LCH. At final follow-up, one patient had been lost to follow-up, two patients had died, three patients had local recurrence, six patients had distant involvement, and 17 patients were alive with disease. The median PFS and OS were 50.5 months (interquartile range (IQR) 23.5 to 63.1) and 60.5 months (IQR 38.0 to 73.3), respectively. Stage (hazard ratio (HR) 4.324; p < 0.001) and chemotherapy (HR 0.203; p < 0.001) were prognostic factors for PFS. Pain is primarily due to segmental instability of the spine from its destruction by LCH. Chemotherapy can significantly improve PFS, and radiotherapy has achieved good results in local control. The LCH lesions in some patients will continue to progress. It may initially appear as an isolated or single-system LCH, but will gradually involve multiple sites or systems. Therefore, long-term follow-up and timely intervention are important for patients with spinal LCH.

Langerhans cell histiocytosis in the glenoid neck with rare mutation: A case report

Langerhans cell histiocytosis (LCH) is a rare disease that occurs mainly in children. It has several forms of clinical presentation. Early diagnosis is important for better results. A 17-year-old male patient presented with right sharp shoulder pain for 2 months. Magnetic resonance image (MRI) of the shoulder showed an expansile osseous lesion in the anterosuperior spine of the right scapula with significant edema that causes compression of the subscapular neurovascular bundle. A CT scan and X-rays were also performed. Overall, all the images suggested a lesion compatible with chondroblastoma; however, the pathology images documented a Langerhans cell histiocytosis with a mutation in the V600E/E2/D in the 15 exon of the BRAF gene. LCH is a difficult diagnosis, especially in cases where clinical presentation is not the most common. This case is unique as the lesion developed not only in the scapula which has a 3% prevalence in LCH, but also had radiographic and MRI characteristics of a chondroblastoma more than the typical LCH lesion. Additionally, it was accompanied by a BRAF V600E mutation which is uncommon in LCHs bone cases.

Targeting of SIRPα as a potential therapy for Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare neoplastic disorder characterized by inflammatory lesions arising from the anomalous accumulation of pathogenic CD1a+ CD207+ dendritic cells (DCs). SIRPα is a transmembrane protein highly expressed in myeloid cells such as DCs and macrophages. Here we show that SIRPα is a potential therapeutic target for LCH. We found that SIRPα is expressed in CD1a+ cells of human LCH lesions as well as in CD11c+ DCs in the spleen, liver, and lung of a mouse model of LCH (BRAFV600ECD11c mouse), in which an LCH-associated active form of human BRAF is expressed in a manner dependent on the mouse Cd11c promoter. BRAFV600ECD11c mice manifested markedly increased numbers of CD4+ T cells, regulatory T cells, and macrophages as well as of CD11c+ MHCII+ DCs in the spleen. Monotherapy with a mAb to SIRPα greatly reduced the percentage of CD11c+ MHCII+ DCs in peripheral blood, LCH-like lesion size in the liver, and the number of CD11c+ MHCII+ DCs in the spleen of the mutant mice. Moreover, this mAb promoted macrophage-mediated phagocytosis of CD11c+ DCs from BRAFV600ECD11c mice, whereas it had no effects on the viability or CCL19-dependent migration of such CD11c+ DCs or on their expression of the chemokine genes Ccl5, Ccl20, Cxcl11, and Cxcl12. Our results thus suggest that anti-SIRPα monotherapy is a promising approach to the treatment of LCH that is dependent in part on the promotion of the macrophage-mediated killing of LCH cells.

Possible involvement of CXCR3-CXCR6 + CD4 + T cells in Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a condition characterized by proliferation of Langerhans cells and wide-range pathologies, ranging from single granulomatous lesions to multi-organ involvement, associated with tissue destruction. LCH pathogenesis remains obscure although association with interleukin (IL)-17A has been reported. We report here a case that illustrates the potential pathogenic role of helper T17 (Th17) cells in LCH-related bone destruction. The patient was a 66-year-old woman. The clinical course included craniectomy and bone mass excision in X-9, diagnosis of LCH confirmed by histopathology, followed by 26-month chemotherapy. In August X, the patient was diagnosed with complete central diabetes insipidus. Symptoms improved after treatment with desmopressin. Pituitary magnetic resonance imaging showed swelling extending from the suprasellar region to the pituitary stalk, suggestive of LCH recurrence. This was followed by chemotherapy combined with mercaptopurine hydrate. RESULTS: Subsequent peripheral blood lymphocyte analysis showed marked increase in activated Th17 cells (CXCR3-CXCR6+ CD4+ T cells). Double staining for CD4 and IL-17 by immunofluorescence of pathological tissue samples obtained during temporal bone mass excision, which confirmed the diagnosis of LCH in X-9, showed areas of combined presence of CD4-positive cells and IL-17-positive cells. Chemotherapy resulted in size reduction of the pituitary lesion and decrease in peripheral blood-activated Th17 cells. We found abundant peripheral blood-activated Th17 cells and high percentages of IL-17-producing cells in osteolytic bone lesions in LCH. This finding, together with the decrease in peripheral blood-activated Th17 cells following chemotherapy, suggests the potential involvement of activated Th17 cells in LCH-related osteolysis.

Multisystemic langerhans cell histiocytosis with orbital involvement

A 3-year-old male initially presented with low-grade fever and scalp rash of 2 months' duration. Patient also showed macrocephaly with bilateral proptosis since birth. Work up revealed CD1a, S100, Langerin and BRAF mutation positive results. A diagnosis of multisystemic Langerhans Cell Histiocytosis (LCH) was confirmed. Multiple punched-out bony lytic lesions with geographic appearance predominantly in the frontal and parietal regions. These are classic radiographic finding for cranial vault lesions in LCH. A solitary lesion may already be suggestive. Langerhans cell histiocytosis is a rare disorder commonly affecting children with unknown etiology. It has multisystemic involvement (skin, lymph nodes, bones, central nervous system, abdominal organs especially the liver and/or spleen). The bones are commonly involved in this disease. That's why biopsy-proven LCH should include a skeletal survey. Langerhans cell histiocytosis can involve any bone in the human body but mainly in the axial skeleton. Over 50% occur in the skull, ribs and pelvis.

Notch-dependent cooperativity between myeloid lineages promotes Langerhans cell histiocytosis pathology.

Langerhans cell histiocytosis (LCH) is a potentially fatal neoplasm characterized by the aberrant differentiation of mononuclear phagocytes, driven by mitogen-activated protein kinase (MAPK) pathway activation. LCH cells may trigger destructive pathology yet remain in a precarious state finely balanced between apoptosis and survival, supported by a unique inflammatory milieu. The interactions that maintain this state are not well known and may offer targets for intervention. Here, we used single-cell RNA-seq and protein analysis to dissect LCH lesions, assessing LCH cell heterogeneity and comparing LCH cells with normal mononuclear phagocytes within lesions. We found LCH discriminatory signatures pointing to senescence and escape from tumor immune surveillance. We also uncovered two major lineages of LCH with DC2- and DC3/monocyte-like phenotypes and validated them in multiple pathological tissue sites by high-content imaging. Receptor-ligand analyses and lineage tracing in vitro revealed Notch-dependent cooperativity between DC2 and DC3/monocyte lineages during expression of the pathognomonic LCH program. Our results present a convergent dual origin model of LCH with MAPK pathway activation occurring before fate commitment to DC2 and DC3/monocyte lineages and Notch-dependent cooperativity between lineages driving the development of LCH cells.

Fine-Mapping of SMAD6 Sequence Data Identifies Additional Putative Risk Loci for Langerhans Cell Histiocytosis

Background: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by lesions including pathogenic CD207+ dendritic cells among an inflammatory infiltrate. Sequencing studies have identified recurrent, mutually exclusive somatic activating mutations in MAPK pathway genes in ~85% of LCH lesions, including BRAF V600E in 50-65%. Despite advances to elucidate the somatic mutational landscape underlying LCH pathogenesis, germline risk factors remain largely unknown. We previously conducted a genome-wide association study of LCH and identified and validated a risk variant in SMAD6 (rs12438941, G->A) associated with a 3.7-fold increase in LCH risk. SMAD6 inhibits bone morphogenetic protein and transforming growth factor-beta (TGF-β)/activin signaling, which are determinants of physiologic myeloid dendritic cell differentiation, and is in close proximity to MAP2K1. Notably, this risk allele is more common in Hispanics, who are at the highest risk of developing LCH, and absent in those of African ancestry who experience the lowest risk of LCH. Our current objective is to further analyze risk of acquiring LCH associated with SMAD6 variations. Methods: Four-hundred and sixty-seven cases diagnosed with LCH were recruited at Texas Children's Hospital. Targeted sequencing of SMAD6 was conducted among cases with ~200x coverage at the Avera Institute of Human Genetics. We accessed aggregate-level SMAD6 sequence data at 940 overlapping loci in SMAD6 from a median of 15,694 non-cancer controls in gnomAD v2.1.1. Variants were pruned using SNPclip due to high linkage disequilibrium (LD; r2 > 0.8) (n = 216 removed), low minor allele frequency (MAF < 0.01) (n = 326 removed), absence from 1000Genomes (n = 240 removed), non-biallelic (n = 3 removed), and absence from dbSNP155 (GRCh37; n = 1 removed). The Fisher's exact test was applied to 154 SMAD6 variants with a Bonferroni critical P-value of 3.2 x 10-4 to assess any association between SMAD6 variation and case status. Sequence data were analyzed in SAS v9.2. Results: In this case-control analysis, 49 variants within SMAD6 were significantly associated with LCH risk (P-values ranging from 4.54 x 10-28 to 2.9 x 10-4), including our previously identified risk locus (P-value: 8.55 x 10-14). Most (48) of the hits were intronic, and one was in the 5' UTR (p = 2.88 x 10-5). The top 4 SNPs had low MAF globally (range 2-9%) but were enriched in the 1000 Genomes AMR (Admixed American superpopulation) population (range 15-23%). The top two SNPs are in high LD in some populations (r2: MXL (Mexican ancestry from Los Angeles) = 0.71, ASW (Americans of African Ancestry in the Southwest USA) = 1.0, PEL (Peruvian from Lima, Peru) = 0.92), but not globally. The third SNP was also in moderately high LD with the peak SNP in some populations (r2: MXL= 0.28, ASW = 0.83, PEL = 0.51). The fourth SNP, which was the variant that was previously identified in our LCH GWAS, has only moderate LD with the peak SNP in some populations (r2: MXL= 0.31, CLM (Colombian from Medellian, Colombia) = 0.3, PEL = 0.13), suggesting that these may be independent signals, and/or that specific SNPs contribute to LCH risk differentially based on ancestry. Conclusions: We identified additional support for associations of germline SMAD6 variants with LCH susceptibility. Our previous risk locus was again enriched among those who develop LCH, and a cluster of loci surrounding our risk locus was identified using this sequence-based approach. Next steps include functional annotation of top hits, analyses to assess whether top hits are associated with LCH patient or clinical characteristics (e.g., genomic ancestry, BRAF V600E mutation status, risk organ involvement), and burden analysis to investigate highly penetrant variants. Overall, this study suggests potential contributions of germline genomics in LCH pathogenesis that may identify a functional role for SMAD6 and account for different incidence rates according to race/ethnicity.

The added value of skeletal surveys in the initial evaluation of children diagnosed with Langerhans cell histiocytosis in the era of staging 18 F-FDG PET/CT: A retrospective study.

Currently, there is no consensus protocol on the initial staging evaluation for Langerhans cell histiocytosis (LCH). Our institutional protocol consists of a skeletal survey and a whole-body positron emission tomography with 2-deoxy-2-[fluorine-18] fluoro-D-glucose integrated with computed tomography (FDG PET/CT) study. The utility of the PET/CT lies in its sensitivity in detecting osseous and extra-osseous lesions, and in determining the baseline metabolic activity of LCH lesions to assess treatment response. However, the added utility of the skeletal survey in staging LCH is unclear. Therefore, this study retrospectively assessed the added diagnostic value of skeletal surveys in patients with baseline PET/CTs for initial staging of LCH. We retrospectively searched the medical records of all patients less than or equal to 18years old at a large children's hospital (May 2013 to September 2021). The inclusion criteria were (a) biopsy-proven diagnosis of LCH and (b) initial staging PET/CT and skeletal survey performed less than or equal to 1month apart. A blinded pediatric radiologist reviewed the skeletal surveys and another reviewed the PET/CTs in identifying LCH osseous lesions. Our study cohort consisted of 49 children with 86 LCH osseous lesions. In non-extremity locations, PET/CT identified 70/70 (100%) osseous lesions, while skeletal surveys detected 43/70 (61.4%) osseous lesions. In the extremities, PET/CT identified 13/16 (81.3%) osseous lesions, while skeletal surveys detected 15/16 (93.8%) osseous lesions. Skeletal surveys increased the detection rate of osseous lesions in the extremities, but added no diagnostic value to the detection of osseous lesions in non-extremity locations. Therefore, we propose to abbreviate the skeletal survey to include only extremity radiographs.

Isolated Scapular Lesion of Langerhans Cell Histiocytosis Detected by 18F-FDG PET/CT.

Langerhans cell histiocytosis (LCH) is a rare disease that occurs mainly in pediatric patients and most adult LCH is considered a part of multisystem or multifocal disease. Only 7.3% of cases present as unifocal bone lesion. Herein, we present a case of an isolated scapular lesion of LCH in a 48-year-old man.

Treatment and Outcomes of Unifocal and Multifocal Osseous Pelvic Langerhans Cell Histiocytosis Lesions in a Pediatric Population.

IntroductionLangerhans cell histiocytosis (LCH) is a rare, clonal disorder characterized by proliferation and tissue infiltration by myeloid dendritic cells, most commonly occurring in pediatric populations. It often manifests as skeletal lesions with possible pelvic involvement. Few studies have characterized and reviewed outcomes after treatment of isolated pelvic LCH lesions.MethodsA retrospective single-institution review was conducted on diagnoses of patients younger than 18 with a diagnosis of unifocal or multifocal skeletal LCH lesions involving the pelvis. Clinical presentations, lesion sites, focal classification, radiographic findings, treatments, complications, and recurrence rates were reviewed.ResultsTwenty patients had unifocal or multifocal LCH pelvic lesions (11 males, nine females). The median age at diagnosis was 3.5 years (0.8-21.6). Eight cases (40%) involved unifocal lesions, and twelve (60%) involved multifocal lesions, with the most common associated skeletal disease occurring at the ilium. 100% of cases had a lytic bone lesion with no pathologic fractures. All cases were treated nonoperatively with chemotherapy medications, corticosteroids, or observation alone. 75% of cases were treated with chemotherapy with a 100% resolution rate. The median length of follow-up was 4.5 years (0.4-16.7). ConclusionOur study found that chemotherapy alone or chemotherapy with corticosteroid supplementation are appropriate options for unifocal pelvic LCH lesions. In contrast, pelvic lesions that are part of a multifocal presentation may be managed adequately with varied chemotherapy regimens. Corticosteroid therapy and observation alone may also be reasonable for a single organ system, multifocal, skeletal lesions that are anatomically accessible for biopsy and small in number or size.

A high-pressure situation

An 8-year-old boy presented with acute visual loss in the right eye and nausea, vomiting, and diplopia. Imaging revealed a right orbital apex mass. Biopsy showed Langerhans cell histiocytosis (LCH), and the patient was diagnosed with isolated orbital LCH causing an orbital apex syndrome. A 12-month cytarabine chemotherapy course was begun, during which the patient developed bilateral optic disc edema. He was diagnosed with cytarabine-induced intracranial hypertension, which was successfully treated with acetazolamide. The cytarabine course was completed with complete resolution of the LCH lesion. The ophthalmologic relevance of this rare disorder is discussed.

Resolution and Re-ossification of Orbital-Wall Langerhans Cell Histiocytosis Following Stereotactic Needle Biopsy.

Introduction Langerhans cell histiocytosis (LCH) is a rare disease that encompasses a spectrum of clinical syndromes. It is characterized by the proliferation and infiltration of white blood cells into organs or organ systems. Reports of management of these lesions have included biopsy, resection, curettage, radiation, and/or chemotherapy. Case Presentation A 40-year-old man presented with a history of right proptosis and retro-orbital pain and was found to have a lytic mass involving the greater wing of the sphenoid extending into the right orbit. A stereotactic needle biopsy using neuronavigation demonstrated this to be LCH. After no further treatment, the mass spontaneously resolved, with virtual normalization of the orbital magnetic resonance imaging at 10 months following the needle biopsy. The bony defect of the temporal bone caused by the mass also re-ossified following the needle biopsy. Discussion This report highlights the potential for an isolated LCH lesion to regress after simple needle biopsy, an outcome only rarely reported previously. Thus, expectant management of such lesions following biopsy or initial debridement should be considered prior to proceeding with additional treatment.

18F-fluorodeoxyglucose-positron emission tomography/computed tomography delineates involved sites in the cervical spine in Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH), a granulomatous tumorous lesion consisting of CD1a-positive clonal immature dendritic cells in association with various inflammatory cells, develops in tissues including bone, skin, lungs, and lymph nodes. When bone LCH exhibits osteolytic lesions, the spine is often involved, and each part of the vertebral body, vertebral arch, and vertebral spinous process can be affected. Such vertebral LCH can occur at the onset of disease and in relapse. To confirm pathological sites, a computed tomography (CT) scan is generally used to characterize lytic lesions of vertebrae, while MRI is suitable for delineating marrow and soft tissue. Additionally, to identify specific locations, 18F-fluorodeoxyglucose-positron emission tomography/CT (FDG-PET/CT) is useful. We describe three LCH cases showing characteristic cervical spinal involvement. Case 1: A 39-year-old woman complained of right temporal pain and was found to have osteolytic lesions of right temporal/sphenoid/petrous bones. She also had central diabetes insipidus (CDI). After the diagnosis of LCH from biopsied tissue, she was treated with chemotherapy and attained remission. Four years later, she complained of neck/shoulder pain associated with herpes zoster in the right arm. PET/CT revealed a cervical spine (C3)-vertical body lesion (Figure 1A). With a revised chemotherapy regimen, she attained a second remission. Case 2: A 70-year-old man, a heavy smoker for more than 40 years, complained of shortness of breath, and a chest X-ray revealed characteristic honeycomb lungs. PET/CT showed hot lesions in the lungs, cervical spine (C3) right vertebral arch (Figure1B), and ribs. Lung lesion biopsy confirmed the diagnosis of LCH. He had no CDI and was treated with irradiation to the cervical spine and with chemotherapy. Case 3: A 40-year-old man who had severe atopic dermatitis since the age of 20 complained of nuchal pain after a traffic accident. He was also noted to have lymphadenopathy in the bilateral axillary and inguinal areas. PET/CT revealed hot signals at the spinous process of the cervical spine (C6) (Figure 1C) and lymph node lesions. Biopsy of the C6 lesion confirmed LCH. He attained a remission treated with chemotherapy and zoledronic acid. Three years later, relapse at the lymph nodes was noted, but not in the C6 lesion. He was treated with chemotherapy for refractory LCH and attained a second remission. An analysis of 76 cases of vertebral LCH by Huang et al. [1] consisted of 40 children and 36 adults, with a male to female ratio of 55:21. Lesions were predominantly in the cervical spine, followed by the thoracic and lumbosacral spines. In an analysis of 30 LCH patients with cervical spine involvement by Jiang et al. [2], 14 had atlantoaxial lesions (C1 and C2), and 16 had sub-axial (C3–C7) lesions. Chemotherapy is recommended for the management of cervical spine lesions in cases of multifocal LCH. In our three cases, two patients had spinal involvement at onset while the other developed it at relapse. All received chemotherapy because of multifocal LCH lesions. In summary, as an imaging study of cervical spine involvement in LCH, PET/CT seems to be useful for pinpointing the involved sites of vertebrae. None The authors declare no conflict of interest.