Like all parts of your body, your bones are living tissue. Your bones undergo remodeling throughout life wherein old bone is removed and replaced by new bone. Bone diseases affect normal growth, development or remodeling leading to weakness and/or deformity. These diseases affect children and adults and occur due to genetic abnormalities, nutritional deficiencies, hormonal disorders, infections and other conditions.
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Your bones normally reach their maximum mass at age 25 to 30 after which they gradually lose density. Osteoporosis is characterized by an abnormal loss of bone mass and deterioration of normal bone structure. This causes bone fragility and an increased risk for fractures. According to a November 2014 study published in the "Journal of Bone and Mineral Research," 10.3 percent of US adults aged 50 or older have osteoporosis and 43.9 percent have low bone mass. Osteoporosis rarely causes symptoms and is often diagnosed only after a fracture has occurred. Regular exercise and adequate calcium and vitamin D intake reduce the risk for osteoporosis. Medications called bisphosphonates help preserve bone mass in people with osteoporosis.
Paget Disease of Bone
Paget disease of bone (PDB) is the second most common bone remodeling disease after osteoporosis. PDB affects approximately 1 to 2 percent of white adults aged 55 or older, according to an April 2009 review article published in "Therapeutic Advances in Musculoskeletal Disease." The condition tends to run in families and rarely occurs in people of African or Asian descent. With PDB, bone resorption and subsequent new bone formation occur at an accelerated rate. This leads to soft, enlarged bones. The spine, pelvis, skull and leg bones are most commonly affected. Although many people with PDB have no symptoms, bone deformities can lead to joint pain, bowing of the legs, headaches and hearing loss. Treatment may include bisphosphonates, orthotic devices and surgery to correct severe deformities.
Osteomyelitis refers to a bacterial bone infection, which can either be acute or chronic. An estimated 50,000 cases of osteomyelitis occur annually in the US, according to Epocrates. Symptoms may include localized bone pain, tenderness, redness and swelling as well as possible fever and chills. Antibiotics are the primary treatment. In some cases, surgery is need to remove infected bone tissue.
Osteogenesis imperfecta is an inherited disease characterized by brittle bones that fracture easily. With each of the 8 types of osteogenesis imperfecta, a defective gene leads to impaired production of collagen, a structural protein necessary for normal bone formation. Osteogenesis imperfecta is typically diagnosed in childhood and affects an estimated 20,000 to 50,000 people in the US, according to the National Institutes of Health. The signs and symptoms of osteogenesis imperfecta vary and may include short stature, loose joints, muscle weakness, spinal curvature, brittle teeth, bone deformity, barrel-shaped chest, hearing loss and a blue or gray tint to the whites of the eyes.
With osteonecrosis, loss of blood supply causes death of bone tissue. The disease most commonly affects the head of the thighbone, or femoral head. The shoulder, knee, wrist or ankle bones can also be affected. An estimated 20,000 to 30,000 people in the US are diagnosed with osteonecrosis of the femoral head each year, as reported in a September 2015 article in the "World Journal of Orthpedics." Most cases of osteonecrosis occur due to bone trauma, such as a hip fracture or dislocation. People with this condition typically develop gradually progressive bone pain. Small areas of osteonecrosis may heal without treatment. For larger bone lesions, treatment may include medication, physical therapy and/or surgery. Total joint replacement is performed if the bone collapses.
Legg-Calvé-Perthes disease is a rare childhood bone disorder similar to osteonecrosis of the femoral head in adults. With this condition, however, the bone typically regenerates in 6 to 24 months.
Most tumors that arise in the bones are noncancerous. The number of people affected by these tumors is unknown as they often cause no symptoms and remain undetected. Cancerous bone tumors are relatively uncommon with an estimated 3,260 new cases per year, according to a 2017 American Cancer Society report. The most common bone cancer is osteosarcoma, which primarily affects children, adolescents and young adults. Metastatic bone cancer, with which cancer from another area of the body spreads to one or more bones, occurs far more frequently. Several of the most common types of cancer often spread to the bones, including lung, breast, prostate and colon cancer. Bone pain and tenderness are common symptoms. Fractures may occur when normal bone is replaced by cancer cells. Treatment for bone tumors depends on the type, size, location and other factors.
Rickets and Osteomalacia
Osteomalacia and rickets are characterized by defective mineralization of the bones, which cause them to be soft and fragile. Rickets affects children and osteomalacia affects adults. These diseases can be caused by a nutritional vitamin D deficiency, or impaired intestinal absorption or metabolism of the vitamin. Children with rickets typically experience stunted growth and bowing of the leg bones. Symptoms common with both rickets and osteomalacia include widespread bone pain and tenderness, and muscle weakness. Treatment typically includes vitamin D supplementation and possibly other therapies, depending on the underlying cause.
Reviewed and revised by: Tina M. St. John, M.D.