BACKGROUND: Disseminated bacillus Calmette-Guérin (BCG) disease is a rare but serious BCG complication in children. Early diagnosis and timely interventions are essential to improve prognosis. However, its manifestations can closely mimic those of Langerhans cell histiocytosis (LCH), which usually leads to a high rate of misdiagnoses. Herein we report the first case of successful application of biopsy tissue metagenomic next-generation sequencing (mNGS) in the differential diagnosis of disseminated BCG disease and LCH.
METHODS: A 5-month-old female infant was transferred to our center for the treatment of paroxysmal cough, intermittent hematochezia and trunk rash. Examination on admission showed moderate anemia, erythropenia, thrombocytopenia and hepatosplenomegaly. The immunohistochemistry of her intestinal biopsy samples showed CD1a (+) and Langerin (+). Genetic testing of both peripheral blood and bone marrow samples suggested BRAFV600E mutation. Hence, she was initially diagnosed with LCH. However, no improvement was observed after a course of systemic chemotherapy. The left axillary lymph node and colonic mucosal biopsy specimens were sent for mNGS which resulted in sequence reads of Mycobacterium bovis-BCG. Triple antimycobacterial therapy was started according to the diagnosis.
RESULTS: The diagnosis of this case was corrected as disseminated BCG disease by mNGS. Currently, she is doing well clinically and continues to follow-up at our outpatient clinic.
CONCLUSIONS: This case suggests that mNGS is a valuable tool in the differential diagnosis of disseminated BCG disease and LCH, which can improve the early diagnosis rate of disseminated BCG disease.

To evaluate the characteristics and treatment outcomes of patients with pediatric Langerhans cell histiocytosis (LCH) with thymic involvement.
We retrospectively described the clinical, biological, and imaging characteristics of a series of 19 patients with pediatric LCH with thymic involvement in our center between September 2016 and December 2019. We further analyzed the treatment response and outcomes of patients treated with chemotherapy or targeted therapy.
Thymic involvement was found in 4.4% of a 433-consecutive pediatric LCH cohort; all LCH-thymic involvement presented with multisystem disease. Patients with thymic involvement were typically younger, harboring more lung and thyroid involvement and less bone involvement than those without thymic involvement. Most patients with thymic involvement had alteration of immunocompetence with decreased numbers of T-lymphocyte subsets and immunoglobulin G levels. Overall, 47.1% of patients demonstrated a response after 6 weeks of induction therapy, and 92.3% of the patients who did not respond to the first-line treatment had resolution of thymus after the second-line and/or targeted therapy. The progression/relapse rate showed no difference between patients who shifted to second-line therapy and those to dabrafenib (33.3% vs 25%, P = 1.000). The survival for patients with thymic involvement did not differ from those without thymic involvement. More patients treated with second-line chemotherapy had severe adverse events than those given dabrafenib (88.9% vs 0, P < .001).
Thymic involvement was observed rarely in LCH and had specific clinical characteristics. Chemotherapy could resolve most thymic lesions, and BRAF inhibitors might provide a promising treatment option with less toxicity for infants with BRAF-V600E mutation.
http://www.chictr.org.cn, identifier: ChiCTR2000030457 (BCH-LCH 2014 study); ChiCTR2000032844 (dabrafenib study).

UNASSIGNED: Langerhans cell histiocytosis (LCH) is a histiocytic proliferative disease without a well-understood etiology. The aim of our study is to summarize the imaging features of PET/MR in children with LCH and to explore its diagnostic role in LCH.
UNASSIGNED: Retrospective analysis was performed of the pretreatment PET/MR imaging data of 15 children with LCH. Comparison of ADC values was done between lesions and normal tissues.
UNASSIGNED: Of the fifteen patients enrolled, five had single-organ or single-system involvement, and ten had multiple-system involvement. Nine patients had varying degrees of bone destruction and increased FDG uptake, whereas thickening and deviation of the pituitary stalk and disappearance of the normal high-signal intensity of T1WI in the neurohypophysis were observed in the pituitary gland in six of them. Splenomegaly with diffuse increased FDG uptake or a normal spleen with increased FDG uptake was found in four cases, liver in three, multiple lymph node enlargement in three, pulmonary lesions in three, and increased metabolism in medullary cavity in two cases. Additionally, two cases involved the skin. Hypermetabolic nodules were detected in muscle in one case, thyroid involvement in one case, and a mediastinal lesion in one case.
UNASSIGNED: PET/MR can show well the distribution of the organs, systems, and lesions involved in LCH and is of considerable significance in the systemic evaluation of LCH.

暂无摘要。

Langerhans cell histiocytosis (LCH) is a neoplasm of myeloid origin characterized by a clonal proliferation of CD1a(+)/CD207(+) dendritic cells. Recurrent BRAF V600E mutation has been reported in LCH. In the present report, we confirm the feasibility of the high-specificity monoclonal antibody VE1 for detecting BRAF V600E mutation in 36/97 (37.1%) retrospectively enrolled patients with LCH; concordant immunohistochemistry and Sanger sequencing results were seen in 94.8% of cases. We then assessed the tumor immune microenvironment status in LCH, and found that the GATA binding protein 3 (GATA3)(+)/T-bet(+) ratio could distinguish between clinical multi-system/single-system (SS) multifocal and SS unifocal LCH. Notably, we found that BRAF V600E mutation is significantly correlated with increased programmed cell death 1 ligand 1 (PDL1) expression and forkhead box protein 3 (FOXP3)(+) regulatory T cells (p < 0.001, 0.009, respectively). Moreover, Cox multivariate survival analysis showed that BRAF V600E mutation and PDL1 were independent prognostic factors of poor disease-free survival (DFS) in LCH (hazard ratio [HR] = 2.38, 95% confidence interval [CI] 1.02-5.56, p = 0.044; HR = 3.06, 95%CI 1.14-7.14, p = 0.025, respectively), and the superiority of PDL1 in sensitivity and specificity as biomarker for DFS in LCH was demonstrated by receiver operator characteristic (ROC) curves when compared with BRAF V600E and risk category. Collectively, this study identifies for the first time relationship between BRAF V600E mutation and a suppressive tumor immune microenvironment in LCH, resulting in disruption of host-tumor immune surveillance, which is DFS. Our findings may provide a rationale for combining immunotherapy and BRAF-targeted therapy for treating patients with BRAF V600E mutant LCH.