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Paget's disease of bone can sometimes lead to further problems.

Bones affected by Paget's disease of bone tend to be more fragile than normal bone and are more likely to break (fracture) – even after a relatively minor injury.

Signs of a fracture include:

• sudden, severe pain
• swelling or tenderness around the injured area
• bleeding, if the bone has damaged the tissue and skin

It's not clear whether bisphosphonate medication helps prevent or treat fractures. If you break a bone, you may need surgery to align the broken bones so that they heal correctly.

Abnormal bone growth can damage nearby cartilage, the spongy tissue that cushions your joints.

This can lead to "wear and tear" of the affected joints (also known as osteoarthritis), which can cause:

• joint pain
• joint stiffness
• swollen joints

Read about how osteoarthritis is treated.

It's common for Paget's disease of bone to affect the appearance of affected bones.

For example, the condition can cause:

• enlarged or misshapen bones
• the legs to curve outwards (bow legs)
• the spine to curve to the sides (scoliosis)
• the upper back to become very hunched over (kyphosis)

As with fractures, it's not clear whether bisphosphonates can help prevent deformities. If they do occur, surgery may be carried out to correct them.

If Paget's disease of bone affects the skull, there's a risk that it could lead to permanent hearing loss and possibly total deafness.

This can occur as a result of damage to the bones or nerves that connect the ears to the brain.

It's not known whether treating Paget's disease of bone helps reduce the risk of losing your hearing, but treatment is usually recommended if the condition is affecting your skull.

The new bone that forms in people with Paget's disease of bone often contains more blood vessels than normal bone, which can mean the heart has to work harder to pump blood around the body.

Very rarely, the heart may not be able to pump enough blood around the body. This is known as heart failure.

Symptoms of heart failure can include:

• shortness of breath
• extreme tiredness and weakness
• swelling in the legs, ankles and feet (oedema)

Heart failure can be treated with medicine and in some cases heart surgery. Read more about how heart failure is treated.

Bone cancer is a rare complication of Paget's disease of bone. It's estimated to affect between 1 in 500 and 1 in 1,000 people with the condition.

Symptoms of bone cancer are similar to those of Paget's disease of bone. They can include:

• bone pain
• swelling around the affected bone
• a lump in the affected bone

Osteosarcoma is a very serious type of cancer that can spread to other parts of the body quickly. But if it's caught early enough, it may be possible to cure it by removing the affected bone.

Read more about how bone cancer is treated.