What is Paget's disease?

Paget's disease of bone (sometimes known by the medical name of osteitis deformans) occurs when the body's bone rebuilding mechanism becomes faulty.

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, causing 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.

Symptoms

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.

Abnormal bone growth in the skull and spine may apply pressure on surrounding nerves which can cause serious problems such as permanent loss of hearing or vision, headaches or nerve damage to the spinal cord. In very rare cases severe Paget's disease may cause heart failure or progress to cancer.

X-rays and a blood test called serum alkaline phosphatase are used to help diagnose the condition. The level of serum alkaline phosphatase is often much higher than normal. Regular blood tests are needed to monitor any changes in the condition. Bone scintiscans are helpful in determining exactly which bones are involved.

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 are equally affected, although the condition is rare in people from Asia, Africa, the Pacific Islands and in Maori.

Causes

The cause of Paget's disease is still unknown. Some researchers believe that the condition may be caused by a genetic predisposition, while others believe that Paget's disease may be a late result of viral infections such as measles. These possibilities are not mutually exclusive.

Treatment of Paget's disease

Paget's disease is treated with medicines called bisphosphonates (sounds like biz - foss- phone- nates). These slow down the faulty bone remodeling process and can depress disease activity for months or years after the medicines are stopped. Treatment does not cure the disease, but can provide long periods of remission.

Bisphosphonate medicines used to treat Paget's disease include the oral tablets alendronate and etidronate, or an injection with either 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 important to take each different bisphosphonate tablet as directed by the doctor or pharmacist: well before the first food of the day, with a full glass of water, long before taking other medicines and to remain upright afterwards for half an hour and until after you have eaten. (This helps prevent side effects such as oesophagitis, inflammation of the passage between the throat and the stomach).

Before the development of bisphosphonates, a medicine called calcitonin was used to slow down the bone remodeling. Calcitonin is not as powerful as the bisphosphonates and does not provide as long a remission.

Pain control using medicines such as paracetamol, non-steroidal anti-inflammatory drugs (known as NSAIDs) may also be helpful. People with Paget's disease also need adequate intake of calcium and vitamin D and individualised exercise programmes which will avoid damaging affected bones.

Surgery may be required either to help fix bone fractures or relieve arthritis by joint replacement.

Original material is written and reviewed by everybody, February 2005.