1.IntroductionLCH is a neoplastic disease arising from an abnormal proliferation of dendritic cells in the bone marrow[1]. It is most common in infants and young children, with an incidence of about 6 cases per million in children under 15 years of age. The adult prevalence rate is about 30% of that of children, with an annual incidence of only 1 to 1.5 cases per million[2, 3]. The clinical manifestations of this disease are diverse and can involve multiple organs and systems throughout the body, and this case is a rare case of single-system single site (SS-s) LCH[4]. The pathogenesis of LCH is still not well understood, but mutations in the BRAF-V600E gene are detected in more than half of the cases, and the remaining BRAF-V600E wild-type cases are likely to have mutations in the MAPK pathway (RAS-RAF⁃MEK⁃ERK) gene loci, including MAP2K1, MAP3K1, ARAF, NRAS, KRAS, NRAS, KRAS[5-8].Isolated esophageal LCH is characterized histomorphologically by clusters and sheets of medium-sized lesion cells with abundant eosinophilic cytoplasm, round or oval nuclei, and reactive inflammatory cells seen in the background[9]. Immunohistochemically, CD1a, Langerin/CD207 and S-100 are positive in LCH, and CD1a and Langerin have high sensitivity and specificity, which are necessary to confirm the diagnosis of LCH[9, 10].In adults with LCH bone is the most common site of involvement followed by skin, lymph nodes and lungs with nonspecific clinical manifestations such as bone pain, skin damage, cough, nausea, headache, weight loss, fever and neuropsychiatric symptoms[11]. Depending on the extent and location of the disease, different treatment strategies may be used. Patients with monofocal disease usually require only localized treatment or observation, whereas patients with multisystem disease require systemic therapeutic treatment. In cases of LCH confined to a single organ, the prognosis is usually excellent, with an overall survival rate of ≥99%[12].Here, we report a case of adult LCH that presented solely with esophagus involvement, without systemic damage.