Bone damage in Langerhans cell histiocytosis is characterized by several features: 1. Bone damage is very common in the disease; about 80%; 2. The most common involvement is in the cranium, especially the top of the temporal bone (osteolysis at multiple points often shows a “map-like” pattern on X-ray); other involvement is common in the mandible, mastoid bone, and postocular bone; 3. Osteolysis Osteolysis is often multifocal and appears slowly, with or without subjective symptoms; 4. The occurrence may be insidious, and may not be detected until after spontaneous fracture or organ function damage. 5, bone marrow involvement is rare, occurring in the late stage of invasive Langerhans cell histiocytosis, manifested as a large number of histiocytic infiltration of the bone marrow, accompanied by symptoms such as platelet drop, leukocyte drop, anemia, etc., which almost always lead to death