Abstract: This article reports the diagnosis and treatment process of a 65-year-old male patient diagnosed with xanthoma dissseminatum. The patient sought medical attention due to reddish brown patchy rashes on the skin of the arms, knees and abdomen. The results of positron emission tomography and computed tomography (PET/CT) suggested that non-Langerhans cell histiocytosis might involve multiple blood vessels, the skin of the posterior neck and right forearm, multiple soft tissues, the descending duodenum and possibly the spine. Biopsy on skin of right arm showed non-Langerhans cell proliferative changes, with a pathological diagnosis of xanthoma dissseminatum. The rash improved after 6 cycles of monotherapy with cladribine. Follow-up PET/CT results indicated that multiple foci of abnormally increased glucose metabolism in the skin, joints, and soft tissues had decreased compared to previous examinations, suggesting disease remission. After stopping medication for 9 months, the patient underwent PET/CT reexamination, which showed new bone lesions. Bone marrow puncture was performed which suggested xanthoma dissseminatum involvement. Subsequently, the patient received chidamide combined with cladribine. By January 2025, the third cycle of chemotherapy had been completed. The patient is still under follow-up.