Our grateful thanks to the Paget's Association for their input to our radio report (that you can hear again further down this page) and for the use of the information below - to learn more and to connect through to the Paget's Association click here.
What is Paget's Disease of Bone? Paget’s disease affects the normal repair and renewal process of bone. Throughout life, bone is renewed and repaired through a process called bone remodelling. Paget’s disease is characterised by abnormalities in this process. The affected bone is renewed and repaired at an increased rate, adversely affecting the bone’s structure. Bone affected by Paget's disease may be enlarged and misshapen.
Paget’s disease can occur in any bone, often causes no symptoms and may be found by chance. For those with symptoms, these may include pain, deformity and fracture. Either single or multiple bones may be affected with common sites being the spine, skull, pelvis and thigh (femur).
The risk of developing Paget’s disease increases with age and it is most commonly diagnosed in those over 50 years. Paget’s disease is the second most common metabolic bone disease after osteoporosis. Approximately 1% of people in the UK, over the age of 55 years, are thought to be affected. The condition is also common in other European countries such as France, Spain and Italy and in people of European descent who have emigrated to other regions of the world, such as Australia, New Zealand, the United States of America and Canada.
How Does Paget's Disease Affect Bone? Bone is an active living tissue that is constantly being renewed through a process known as remodelling. Cells called osteoclasts break down old, damaged bone to make way for new bone laid down by cells called osteoblasts. Over time, this bone is mineralised, forming a hard and strong skeleton.
Under normal circumstances, the amount of bone removed is balanced by the amount of bone laid down. In Paget’s disease, the processes of bone resorption and bone formation are markedly increased. The osteoclasts are larger than normal and break down bone faster than normal. The osteoblasts respond to this by depositing new bone at an increased rate. This dysregulation of bone turnover in Paget’s disease results in abnormalities of the bone structure, weakening of the bone and enlargement or deformity of the affected bones. Pagetic bone often appears misshapen and enlarged.
What Causes Paget's Disease? There are still some uncertainties about the causes of Paget’s disease, but it is generally believed to be due to a combination of genetic and environmental influences.
Genetic factors play a key role in predisposing to Paget's disease. It is thought that people who develop Paget’s disease inherit variations in one or more genes that regulate osteoclast activity, causing bone resorption to be increased. This is thought to be responsible for the increased bone remodelling that is typical of the disease. The most important predisposing gene for Paget’s is called Sequestosome 1 (SQSTM1). Abnormalities of SQSTM1 have been identified in 40% to 50% of people with a family history of Paget's disease and also in 5% to 10% of people who have no family history. The children of people with Paget’s disease are about seven times more likely to develop Paget’s disease than people who don’t have a family history.
Environmental factors also play a role in Paget’s disease, as evidenced by the fact, that over the last few decades, the frequency and severity of the disease have declined in many countries, and is most marked in regions that previously had a high prevalence, such as the UK. Various environmental triggers have been suggested, including dietary calcium or vitamin D deficiency, exposure to environmental toxins, repetitive mechanical stress on the bone, skeletal trauma and slow viral infections. Despite this, researchers have yet to discover which environmental factors influence the development of Paget’s disease.
The Symptoms of Paget’s. Many people who have Paget’s disease do not have symptoms and never develop complications. In many cases, individuals are unaware that they have the condition. It may be discovered by chance on x-ray or if a blood test is performed for another reason.
Of those who present with symptoms, pain is the most common. Pain may arise from the affected bone itself, or from the altered biomechanics of limb deformity; for example, a bowed leg alters the way you walk and puts stress on the joints and soft tissues.
The blood flow to active areas of Paget’s disease increases and this can lead to a feeling of warmth over the affected bone. The affected bone may become enlarged and misshapen.
In many cases there may be no symptoms and individuals are unaware that they have Paget’s disease.
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