I. Introduction Langerhans Cell Histocytosis (LCH) is an abnormal differentiation of histiocytes characterized histologically by bone destruction, Langerhans cell proliferation and eosinophilic cell infiltration. Eosinophilic Granuloma (EG), Hand-Schűller-Christian Disease, and Letterer-Siwe Disease. The Department of Radiotherapy, Henan Provincial People’s Hospital, Niu Po 1. Classification Eosinophilic granuloma is the most familiar and common among orthopedic surgeons. EG refers to a single bone LCH with the best prognosis; multiple occurrences are rare (Figure 1). Han-Sue-Ker disease is a bone defect with endocrine abnormalities (typically manifested as a triad: ophthalmoplegia, uveitis, and osteolytic destruction of the skull). Lecher’s disease is associated with visceral damage and has a poor prognosis.2. Pathogenesis 3. Incidence The incidence of LCH is about 1/1.5 million, of which 79% are single EG, 7% are multiple EG, and 14% are other types of LCH. LCH occurs in children and adolescents, and the age of onset is 5 to 10 years. In recent years, the proportion of adult cases reported in large numbers abroad is much higher than expected, at about 39%-58%. In adult patients, the ratio of men to women is as high as 5:1.4. Distribution Therefore, spinal eosinophilic granuloma is rare, accounting for 6.5-25% of the bony damage of LCH.5. Prognosis The prognosis of spinal eosinophilic granuloma is good, with a single lesion healing spontaneously and a low recurrence rate. 30 cases of cervical LCH (follow-up rate: 85.7%) followed up at the North Medical College, with a mean follow-up of 53.5 months, and no recurrence cases were seen. The recurrence rate of multiple spinal LCH was only 3.6%. The diagnosis of spinal LCH is still based on the triad of “clinical manifestations + imaging + pathological biopsy”.1. Clinical manifestations Spinal LCH lacks typical clinical symptoms. 80% of patients complain of localized dull pain and limited movement without neurological symptoms at the first visit. A few patients have fever, and some patients are found to have kyphosis or scoliosis, pathological fracture of the spine, or other manifestations of LCH; 37% of cervical LCH can manifest as a sloping neck. Some patients have sensory and motor dysfunction due to irritation or compression of the spinal cord or nerve roots. 2. imaging: early vertebral osteolytic changes are often followed by compression fractures – forming “flattened vertebrae” in children. 3. pathological examination The efficiency of puncture biopsy is as high as 94%. Microscopic typical LCH is characterized by a large number of Langerhans cells in patches and a large number of eosinophilic infiltration (limited granuloma formation), which can be mixed with lymphocytes, neutrophils and plasma cells. Specific Birbeck granules seen by electron microscopy or immunohistochemistry showing positive for specific antigens CD1a and S-100 are important diagnostic factors. The vast majority of patients with EG have a good prognosis and can be treated satisfactorily with conservative therapy. Treatment is mainly surgical excision of the mass, followed by radiotherapy, or radiotherapy alone. A common group of tumors in children is called histiocytic proliferative disease X, which includes Han-She-Co disease, Le Scheur disease, and eosinophilic granuloma, the latter being the best treated of these three diseases with the best prognosis. Radiation therapy is usually curative. Moreover, the dose of radiotherapy in children is extremely low and has less impact on the development and growth of the affected bone. Chemotherapy is required if there are multiple occurrences throughout the body. The disease is often confused with lymphoproliferative eosinophilic granuloma and a clinical pathological diagnosis is necessary to differentiate it.