Danger level: Medium

What is it?

Paget disease is a condition that affects the growth of bones, causing them to be enlarged and deformed.

Who gets it?

In the US, Paget disease affects 3-4% of people older than 40 (it’s uncommon before age 45). It’s more common in African Americans (and rare in Asians).

Paget disease is almost twice as common in men than in women.

What causes it?

Even though we all know bones as hard, rigid and unliving things, they are actually a living tissue like any other tissue in our body. They constantly grow and break down. Cells in the bones named osteoblasts are responsible for growing the bone, while cells called osteoclasts are responsible for breaking it down, so that in the end the result is an even bone.

In Paget disease, this breakdown of bones is faster than normal, and to keep up with it, the body builds bone much faster. The problem is that the new bone which was built in such a hurry is weaker and more brittle, which causes it to break more often. The bones which are most involved in the disease are those in the pelvis, the spine, the skull, the arms and the legs.

The cause for this phenomenon is unknown. It might be related to a genetic cause or to viruses.

Paget disease affects the bones. Photo by D’arcy Norman

How does it feel?

Most people don’t feel anything. When they do, the symptoms have something to do with the defective process in the bones:

1. Pain – It can develop from a bone that’s affected by the disease or from complications such as inflammation of the joints (arthritis).
2. Fractures – Since the new bone that develops in the disease process is weaker, fractures are more common.
3. Deformities in the bones – When the bone breaks down and builds up properly, the new bone that forms is even. In Paget disease, the new bone doesn’t grow naturally, and so it’s distorted or deformed. For example, the legs may get a bow shape or the skull may be bigger.
4. Related problems – The growth of bone in the skull can cause things related to its location – such as problems with hearing, since the new bone presses on a nerve. When it’s near the spine, it can cause weakness. And so on, depending on the area where the disease is.

How is it discovered?

Usually, since most people have no symptoms of the disease, it’s discovered by chance when you go to a doctor for a different reason. There are two ways to discover it:

1. By an X-ray image – The thickening or deformity of the bones will be seen. You can see an example of such a deformity here.
2. By a blood test – The cells responsible for bone creation (osteoblasts) produce an enzyme (a molecule that’s responsible for reactions in the body) called ALP. Since these cells work overtime, the level of this enzyme will be high.

How is it treated?

The main treatment is with drugs called bisphosphonates – they inhibit the osteoclast cells, which in turn inhibits the breakdown of the bone. Another treatment are pain killers.

If a joint was affected by a nearby disease, a surgery might also be needed to replace the joint.

What happens after treatment?

If treatment is started before any bone deformities occur, the outlook is usually good.

In less than 1% of people with Paget disease, tumors of the bone might develop with time (both cancerous and noncancerous).

The bottom line: How do I avoid it?

There is no known way to avoid it. You can, however, avoid the complications by taking the treatment.

What next?

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