The Bone Disease You’ve Likely Never Heard Of

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By Lisa Shah, MD and Vinita Singh, MD

Although it is the most prevalent bone disease in America after osteoporosis, chances are you’ve never heard of Paget’s disease.

Also known as osteitis deformans [oss-tee-EYE-tis dee-FOR--manz], Paget’s disease is a chronic condition named after English surgeon and pathologist Sir James Paget, who first described the condition in 1877. It occurs when the body’s breakdown and reformation of bone – a constant process in which cells called osteoclasts clear out old bone and cells called osteoblasts replace it with new bone – is not functioning properly. Bone is broken down faster than normal by the osteoclasts, triggering the osteoblasts to keep up with the pace. The result is bone that is placed in a more irregular, haphazard fashion, leading to bone enlargement and deformity. Plus, the new bone is more fragile and consequently is more prone to fracture than normal bone.

Paget’s can affect a single bone or involve multiple bones. The most frequently affected bones are the pelvis, vertebra, skull, femur (the thigh bone) and tibia (shin bone). It’s rarely diagnosed in people under the age of 40, but affects an estimated 2 to 3 percent of the general population over the age of 55. Although the cause of Paget’s disease is unknown, genetics is thought to play a role, as Paget’s can run in families. In addition, researchers have also found a possible link between Paget’s disease and viral infection.

Most Paget’s patients are unaware they have the disease, since they are often asymptomatic. The disease is usually discovered incidentally when tests are performed for another reason, such as x-ray imaging, which would reveal areas of porous, thickened bone, or blood tests, which would reveal an elevated level of the enzyme associated with bone cell formation.

Common symptoms of Paget’s disease include bone deformities and bone pain, which can be due to bony overgrowth or fracture or arthritis of the nearby joints, and is usually mild to moderate in intensity, dull and aching in quality and typically occurs throughout the day, but often worsens at night.

Other, less–common manifestations of Paget’s disease are headache, hearing loss, paralysis, kidney stones and congestive heart failure. Headache and hearing loss can occur when Paget’s disease involves the skull, as the enlarged skull bones can compress nerves and cause damage to the inner ear. Damaged vertebra may pinch spinal cord nerves, causing pain, numbness, tingling, weakness, or, very rarely, paralysis in the legs. Kidney stones are due to elevated calcium levels in the blood. And heart problems are caused when a lot of bone area is involved in a person with Paget’s disease, causing an increase in blood vessels that can strain the cardiovascular system.

When Paget’s disease is suspected, initial testing includes a plain x-ray of the bone which can show bony lesions, overgrowth and deformities. A bone scan is more sensitive than an x-ray, especially in identifying early disease. It helps determine the extent of the disease and may also identify the affected bones. In advanced cases, a CT scan or magnetic resonance imaging (MRI) test can be performed. Also, a blood test called bone-specific alkaline phosphatase can indicate high bone turnover. These blood tests are also helpful in monitoring the response to the treatment and following the evolution of the disease in untreated patients.

Treatment for Paget’s disease is required if you are experiencing symptoms, are at risk for future complications, or are having surgery involving Paget-affected bone. The decision to treat Paget’s with medication is based on balancing potential benefits with potential adverse events.

Medical treatment involves administering a class of medication called bisphosphonates that work to regulate the cells that remove old bone and permit more normal bone growth. There are oral and injectable formulations available, and frequency of treatment is dependent on which medication is chosen and how your body responds to that medication. In many patients treated with medication, Paget’s disease can go into remission for years. However, remission is not guaranteed and recurrence of the disease can occur at any time, which is why continued follow-up with your physician is important. Treatment can control Paget’s disease and lessen symptoms, but does not cure Paget’s disease.

Whether or not treatment is required, monitoring is necessary to prevent complications such as fractures. Laboratory tests are used to monitor Paget’s disease and assess for response to treatment.

The prognosis for most people with Paget’s disease is generally good, particularly when treatment is given before major changes in the affected bones have occurred.