Paget's disease of the bone occurs when a fault develops in your body's normal bone rebuilding process.
Over time, Paget's disease can cause weak and deformed bones leading to pain, possible nerve and joint damage and other complications. Treatment with medicines can slow the progression of the disease. In some cases, other treatments such as surgery may be needed.
Bone is a living tissue that is constantly being broken down and rebuilt – a process called "bone remodelling". Bones affected by Paget's disease have a disorganised remodelling process which means the structure, or architecture of the bone is not rebuilt properly. This causes weak bones which may be deformed, overgrown, bowed or prone to breaking easily.
Paget's disease can occur in any bone in the body. One-third of patients have only one affected bone, but the average number is about three. The bones most often involved include the pelvis, spine, skull and the long bones in the arms and legs.
Image credit: Anatomy & Physiology, Connexions Web site
The cause of Paget's disease is still unknown. Some researchers believe the condition may be caused by a genetic predisposition, and it is thought that people who have a relative with Paget's disease may be more likely to develop the condition themselves. Researchers are also looking into the possibility that Paget's disease may be a late result of viral infections such as measles.
Who gets Paget's?
Up to 3% of people of European origin over the age of 40 may be affected by Paget's disease, and the prevalence increases as people age. Men and women can both be affected, although the condition is rare in people from Asia, Africa, the Pacific Islands and in Māori.
Symptoms associated with Paget's disease include pain around the affected bone and osteoarthritis if the disease occurs near bone joints. Bone pain associated with Paget's disease is usually described as continuous, and unlike osteoarthritis, is often worse with rest and at night. Other symptoms include:
- Abnormal bone growth in the skull may apply pressure on surrounding nerves which can cause problems such as hearing loss and headaches.
- Rarely, vision may also be affected by nerve damage in the skull.
- Abnormal bone growth in the spine can cause problems such as curvature of the spine and nerve damage to the spinal cord.
- In rare cases, severe Paget's disease may cause heart failure and very rarely may progress to cancer.
To diagnose Paget's disease, x-rays and a blood test called a serum alkaline phosphatase are used. The level of serum alkaline phosphatase is often much higher than normal in a person with Paget's disease. Regular blood tests are needed to monitor any changes in the condition. Bone density scans are helpful in determining exactly which bones are involved.
Paget's disease is treated with medicines called bisphosphonates (sounds like: biz-foss-phone-nates). These slow down the faulty bone remodelling process and can suppress disease activity for months or years after the medicines are stopped. Treatment does not cure the disease, but can provide long periods of remission.
Bisphosphonates: Bisphosphonate medicines used to treat Paget's disease include oral tablets (e.g. alendronate and etidronate), or an injection (e.g. pamidronate or zoledronic acid). Courses of oral tablets are usually prescribed for six months and treatment may be repeated if the disease relapses. These tablets may cause stomach and gut side effects such as indigestion and heartburn, as well as muscle or joint pain and headaches.
It is very important to take each different bisphosphonate tablet as directed by your doctor or pharmacist. There will be specific instructions about when to take the tablet, how long to wait before having other medicines and food, and you will probably be asked to stay upright (not lie down) for a period after taking the tablet. Make sure you follow the instructions you are given carefully, as this will help to prevent any side effects.
Calcitonin: Before the development of bisphosphonates, a medicine called calcitonin was used to slow down the bone remodelling. Calcitonin is not as powerful as the bisphosphonates and does not provide as long a remission.
Pain relievers: Pain control medicines such as paracetamol or non-steroidal anti-inflammatory drugs (known as NSAIDs) may also be helpful. Seek advice from your doctor or pharmacist about the best pain relief medications for you. Individual factors such as other medical conditions you may have and other medicines you take, mean some pain relievers may not be suitable.
Surgery: Surgery may be required either to help fix bone fractures or relieve arthritis by joint replacement.
People with Paget's disease also need adequate intake of calcium and vitamin D and individualised exercise programmes which will avoid damaging affected bones.