Langerhans cell histiocytosis (LCH) is a rare disease most commonly presenting in the pediatric population and characterized by neoplastic clonal proliferation of Langerhans dendritic cells with accumulation in various sites, including skeletal and visceral lesions.1 There are three levels of classification per the Histiocyte Society: single-system single-site (SS-s), single-system multiple-site (SS-m), and multisystem (MS).2 SS-s predominantly carries a better prognosis with more conservative treatment while MS requires a more aggressive treatment that is more likely to have an inferior outcome. While the extremities are not uncommon sites of unifocal or multifocal lytic lesions due to LCH, few studies have characterized and reviewed the eventual outcomes after treatment at these sites in a pediatric population. Recently Mavrogensis et al 3 reviewed 66 SS-s treated exclusively with steroid injections and biopsy alone with excellent outcomes. Information regarding treatment and long-term sequelae at these sites is lacking. This study aims to (1) clinically and radiographically characterize a series of unifocal (SS-s) and multifocal (SS-m) LCH lesions in the appendicular skeleton and (2) determine the success and recurrence rates with different treatment modalities in a pediatric population at a tertiary children’s hospital. We obtained institutional review board approval for a retrospective analysis of patients younger than 18 years old with a diagnosis of LCH at Texas Children’s Hospital before June 1, 2021. Inclusion criteria included patients with a unifocal or multifocal skeletal lesion. From these, patients with appendicular lesions were selected. Exclusion criteria included bone marrow involvement, multisystemic disease, including patients with visceral or organ involvement, other malignant diagnoses, insufficient patient data, or patients with under 6 months of follow-up. Six hundred and eighty-six patients diagnosed with LCH from January 1, 1999 to June 1, 2021 were reviewed. The most common reasons for exclusion were multisystemic cases. Patients underwent a skeletal survey and …

中文翻译：

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儿科人群单灶性和多灶性骨性阑尾朗格汉斯细胞组织细胞增多症的表现、治疗和结果

朗格汉斯细胞组织细胞增生症 (LCH) 是一种罕见疾病，最常见于儿科人群，其特征是朗格汉斯树突状细胞的肿瘤性克隆性增殖，并在不同部位积聚，包括骨骼和内脏病变。1 根据组织细胞学会的分类，分为三个级别：单系统单点 (SS-s)、单系统多点 (SS-m) 和多系统 (MS)。2 SS-s 主要通过更保守的治疗带来更好的预后，而 MS 需要更积极的治疗更有可能产生较差结果的治疗。虽然四肢是 LCH 引起的单灶性或多灶性溶解性病变的常见部位，但很少有研究描述和回顾儿科人群在这些部位治疗后的最终结果。最近，Mavrogensis 等人 3 回顾了 66 例 SS-s，仅通过类固醇注射和单独活检治疗，结果非常好。缺乏关于这些部位的治疗和长期后遗症的信息。本研究旨在 (1) 在临床和影像学上表征阑尾骨骼中的一系列单灶 (SS-s) 和多灶 (SS-m) LCH 病变，以及 (2) 确定儿科不同治疗方式的成功率和复发率三级儿童医院的人口。我们获得了机构审查委员会的批准，可以对 2021 年 6 月 1 日之前在德克萨斯儿童医院诊断为 LCH 的 18 岁以下患者进行回顾性分析。纳入标准包括患有单灶或多灶骨骼病变的患者。从这些患者中，选择了有四肢损伤的患者。排除标准包括骨髓受累、多系统疾病（包括内脏或器官受累的患者）、其他恶性诊断、患者数据不足或随访不足 6 个月的患者。对 1999 年 1 月 1 日至 2021 年 6 月 1 日期间诊断为 LCH 的 686 名患者进行了回顾。最常见的排除原因是多系统病例。患者接受了骨骼检查并……