Bone pain is a very common clinical manifestation of hematologic disease. Bone pain most often occurs in the thoracic ribs, vertebrae, and also in the long bones of the extremities. The pain can be dull or severe and unbearable. What blood disorders can cause bone pain and why does it occur? Blood diseases that can cause bone pain include leukemia, multiple myeloma, bone marrow necrosis, lymphoma, and Langerhans histiocytosis. 1. Leukemia Both acute and chronic leukemia can manifest as bone pain. Bone pain occurs because the bone marrow cavity has limited capacity and the bone around the cavity is hard and inelastic, while the proliferation of leukemia cells in the bone marrow in leukemia makes the tension in the bone marrow cavity much higher and causes pain. In addition, leukemia cells can also infiltrate and destroy the cortex and periosteum of bones, which can also cause and aggravate bone pain. Bone pain in leukemia is most common in the thoracic ribs, and sternal pressure pain is often one of the characteristic signs of leukemia. Most leukemia bone pains are vague and dull. In a few patients, the bone pain is severe and unbearable. Acute lymphoblastic leukemia in children can have severe pain in the long bones of the extremities, which cannot be relieved by general painkillers, even pethidine. Although the skeletal pain is severe, the examination is normal and there is neither local redness nor swelling, nor change in skin temperature. 2.Multiple myeloma Bone pain is one of the main symptoms of the disease. The cause of bone pain is different from that of leukemia, and it is caused by the destruction of bones. Multiple myeloma is a malignant neoplastic disease caused by malignant transformation of plasma cells in bone marrow. The malignant plasma cells are called myeloma cells, which can secrete a cytokine called osteoclast-activating factor. This osteoclast-activating factor can stimulate osteoclasts, which can greatly enhance the function of osteoclasts, leading to bone calcium loss, osteoporosis and bone destruction. Bone pain in multiple myeloma is most common in the lumbosacral region, followed by the thoracic ribs, and less common in the long bones of the extremities. The pain varies in severity and is often mild and temporary in the early stage, and can be triggered or aggravated by activities. In addition, multiple myeloma is prone to pathological fractures due to bone destruction, and if a fracture occurs, the bone pain suddenly increases and becomes severe. When examining patients with multiple myeloma, sometimes localized bone masses can be found, and local bone pressure pain can be obvious. 3.Lymphoma Bone pain can occur when lymphoma cells invade the bone. The pain is usually limited to the lesion site, and localized pressure pain can be evident. The main bones invaded by lymphoma are thoracic vertebrae, lumbar vertebrae, ribs, pelvis, femur and cervical vertebrae in order. The pain is usually vague and dull, but there may be episodes of severe pain. 4. Langerhans histiocytosis, originally called histiocytosis X, is a group of histiocytic proliferative disorders of unknown origin. The disease can involve multiple tissues and organs, and the diagnosis relies on pathological examination of the lesion site to find histiocytic infiltration. The disease can develop in all age groups, but more than 50% are children aged 1-15 years. Bone lesions occur in almost all patients and are mainly osteolytic, either in a single site or in multiple sites. Bone destruction causes skeletal pain and can be accompanied by local redness and swelling, and maxillofacial bone destruction not only has pain, but also can have loose teeth and even tooth loss. 5, bone marrow necrosis is relatively rare. Due to the unclear cause, a large number of cells in the bone marrow dissolve and necrosis in the short term, producing severe bone pain, which is very intense and unbearable. All pain medications are difficult to stop the pain. Most cases of bone marrow necrosis are secondary to other malignancies, while others have no clear cause.