What is Paget’s disease of Bone?
Paget’s disease is known as a bone remodeling disorder. Bone may seem like a very inactive tissue, but this is not the case. Bone is constantly undergoing ‘turnover’ or replacement. New bone is formed, and old bone is absorbed. This process is known as bone remodeling.
In most people this remodeling process occurs without problems. However, the process can go awry and create abnormalities of the bone. In Paget’s disease, the bone remodeling process is disregulated. New bone is placed where it is not needed, and old bone is removed where it is needed. This disregulation can distort the normal skeletal architecture.
What causes Paget’s disease?
The cause of Paget’s disease is not entirely known, but it is thought to be caused in part from a childhood virus. A virus particle, known as a paramyxovirus nucleocapsid, has been identified within the bone cells of individuals with Paget’s disease. This virus particle is not found in normal bone. While this relationship has been identified, a clear connection between the virus and the cause of Paget’s disease is not known.
Paget’s disease is more common in certain geographical locations, specifically England, Western Europe, and the United States. It is very uncommon in Scandinavia, China, and India. Paget’s disease is most commonly diagnosed in the sixth decade, and increases in prevalence as age increases. Paget's disease is very uncommon in individuals under 40 years of age. In most cases, Paget’s disease is a mild disease that does not cause any problems or complications. In fact, about 80% of individuals are diagnosed with Paget's disease following an x-ray performed for an unrelated reason.
What are the symptoms of Paget’s disease?
In individuals who do experience symptoms from Paget’s disease, the most common complaints relate to bone or joint pain. Other common symptoms include swelling of joints, tenderness or redness over the affected areas, and occasionally individuals will not know of Paget’s disease until experiencing a fracture through a weakened area of bone. The most common bones affected by Paget’s disease are the pelvis, femur (thigh bone), spine, skull, and tibia (shin bone).
Diagnosis of Paget's disease is made by physical examination, x-rays, and laboratory studies. The physical examination may show abnormalities of the skeletal shape or bone deformities. X-rays commonly show abnormalities of bone turnover, including areas of increased and areas of decreased bone deposition. Laboratory studies will invariably show an increased level of alkaline phosphatase, a byproduct of bone formation. Calcium levels within the body are usually normal.
