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.
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 significant 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.
Too much calcium in the blood
In rare cases, the increased cycle of bone renewal in Paget's disease of bone can result in calcium building up in the blood. This is known as hypercalcaemia.
It usually only occurs in people who have been confined to bed after an operation or a fracture.
Symptoms of hypercalcaemia can include:
new or worsening bone pain
Hypercalcaemia can be treated using medicines to lower blood calcium levels and slow down bone regeneration.
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 occasionally, 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 100 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:
swelling around the affected bone
a lump in the affected bone