Paget's disease of bone

Bone is constantly renewed, with old bone broken down and new bone laid down in balance. In Paget's disease this renewal becomes overactive and disorganised in one or more areas, so the bone is rebuilt faster but in a weaker, less orderly structure. Why this happens is not fully understood. There is often a genetic element, and the condition can run in families, so a close relative being affected is a recognised association. It becomes more common with age and is unusual before the age of 50. It affects both men and women, and characteristically involves certain bones, such as the pelvis, spine, skull and long bones of the leg, rather than the whole skeleton.

Many people with Paget's disease have no symptoms at all. Where it does cause them, features may include:

• Bone pain in the affected area, such as the pelvis, spine, skull or long bones of the leg
• Changes in the shape of a bone, or bowing of a limb
• Joint pain if a nearby joint is affected
• In some cases, complications related to the affected bone

Paget's disease is often first suspected from a blood test showing a raised level of a bone enzyme, or found incidentally on an X-ray done for another reason. The diagnosis is confirmed with imaging, and sometimes a bone scan to show which bones are involved. Assessment also looks at whether the affected bone is causing or likely to cause problems.

Not everyone needs treatment, particularly if there are no symptoms and no bone at risk. Where treatment is needed, the main medicines are bisphosphonates, which control the overactive bone turnover; this is most often a single infusion of zoledronic acid, given under specialist supervision. Calcium and vitamin D are checked first and corrected if needed, because vitamin D should be adequate before an infusion to avoid the calcium level dropping afterwards. The bone enzyme on the blood test (alkaline phosphatase) is then monitored to judge the response. Pain relief and management of any complications are addressed alongside this. Bone health more generally, including osteoporosis, is considered as part of the assessment. The plan is agreed with you.

Most people with Paget's disease live entirely normally, and the outlook is generally very good. A few simple measures help.

• Keep your calcium and vitamin D adequate through diet and, where advised, supplements, as this supports bone health and treatment.
• Stay active, since regular weight-bearing exercise helps keep bone and muscle strong; ask if any activity should be modified where a leg or the spine is affected.
• Attend your follow-up blood tests and reviews, so the affected bone and your response to any treatment can be tracked.
• Look after joints near an affected bone, as wear can occasionally develop there over the years.

Because Paget's shares ground with wider bone health, the assessment also keeps an eye on osteoporosis and overall metabolic bone disease.

Most changes in Paget's disease are slow, but some symptoms warrant prompt attention. Arrange a routine review if you notice new or worsening bone pain, increasing bowing or change in the shape of a limb, or pain in a joint next to an affected bone.

Seek more urgent medical advice if you develop:

• Sudden, severe pain in an affected bone, or pain following a minor knock, which could indicate a fracture
• New numbness, tingling, weakness or problems with bladder or bowel control, especially where the spine is involved
• Changes in hearing, or persistent headache, where the skull is affected

These features do not mean something serious is certain, but they should be checked rather than waited out, so the cause can be identified and managed promptly.

Paget's disease is very manageable, and assessment determines whether treatment is needed and monitors the affected bone. If you have unexplained bone pain, a raised bone enzyme on a blood test, or a bone change found on a scan, a specialist review can clarify it.

How is Paget's disease of bone diagnosed?

It is often first suspected from a blood test showing a raised level of a bone enzyme called alkaline phosphatase, or spotted by chance on an X-ray taken for another reason. The diagnosis is then confirmed with imaging, and sometimes a bone scan to map which bones are involved. Assessment also considers whether the affected bone is causing, or likely to cause, any problems, so the right plan can be agreed with you.

Does Paget's disease of bone always need treatment?

Not always. Many people have no symptoms and no bone judged to be at risk, and in that situation careful monitoring may be all that is needed rather than medication. Where treatment is appropriate, the aim is to control the overactive bone turnover and ease symptoms. The decision rests on whether you have bone pain, which bones are affected, and the risk of complications, and it is always discussed and agreed with you.

What does treatment for Paget's disease involve?

The main medicines are bisphosphonates, which calm the overactive bone renewal. This is most often a single infusion of zoledronic acid given under specialist supervision. Beforehand, your calcium and vitamin D are checked and corrected if needed, as vitamin D should be adequate to avoid the calcium dropping after the infusion. The alkaline phosphatase blood level is then monitored to judge how well it has worked, alongside pain relief where required.

What can I expect after treatment, and is the outlook good?

The outlook is generally very good, as Paget's disease is very treatable. After a bisphosphonate infusion, the bone enzyme on your blood test usually falls over the following months, which reflects the bone turnover settling, and many people notice their bone pain ease. Repeat treatment is not always needed straight away. We follow up with blood tests and review so any change can be picked up and managed early.

How does Paget's disease differ from osteoporosis?

They are different conditions, though both affect bone and can occur together. Osteoporosis is a general thinning of bone that raises the risk of fractures, usually without pain unless a bone breaks. Paget's disease disrupts the normal renewal of specific bones, so they may become weaker, larger or change shape, and can cause localised bone pain. Both are assessed as part of a wider look at your bone health, and each is very manageable.