Paget's Disease

What is Paget’s disease?  What are the causes?   

            Paget’s disease (osteitis deformans) is a bone disorder of increased bone destruction and formation that eventually weakens the bone.  Normally, bone formation begins as an orderly process of bone destruction by cells called osteoclasts. Then cells called osteoblasts reform the bone.  Throughout life, the processes of bone formation and destruction occur in harmony to maintain bone strength in an organized fashion.  However, in some individuals there is an accelerated rate of bone destruction followed by disorganized bone formation, which weakens the structure of bone.

While the exact etiology of Paget’s disease in unknown, there is an increased incidence of the disease among family members leading many to believe that there may be a genetic component.  For instance, first-degree family members of patients with Paget’s disease are seven to ten times more likely to develop the disease. Some studies have also shown a viral component to the disease etiology, even though a specific virus has not been isolated.  It is possible that a viral particle triggers the disease in genetically predisposed individuals.

What are the symptoms of Paget’s disease?

Paget’s disease is more commonly asymptomatic, but may exhibit a variety of nonspecific symptoms due to increased bone turnover.  The bones that are more commonly affected include the pelvis, spine, skull, and long bones.  Individuals may experience any or a combination of the following symptoms:

• Bone pain
• Factures
• Skeletal deformities – bowed legs, gait changes, fronto-occipital skull enlargement
• Warm sensation – due to increased blood supply to abnormal bones
• Nerve damage – hearing loss, visual abnormalities
• Cardiac abnormalities – shortness of breath

How is Paget’s disease diagnosed?

Most patients are asymptomatic, so diagnosis is often times incidental.  For example, the disease may be suspected when a routine blood test shows an isolated elevation of alkaline phosphatase (AP), an enzyme associated with increased bone formation.  Although elevated alkaline phosphatase is a nonspecific finding, it is frequently elevated in patients with Paget’s disease.   The disease may also be suspected when radiographic study undertaken for another reason shows evidence of the disease.

If Paget’s disease is suspected in a patient, radiographic studies can be obtained to identify abnormal bones.  The most sensitive study is a bone scan in which radioactive particles are preferentially absorbed by bones with an increased metabolic rate.   These areas of increased uptake (known as “hot” spots) can be further studied with plain radiographs.

How is Paget’s disease treated?

            In most patients, the disease is asymptomatic and requires no treatment.  However, those with symptoms or complications of the disease may get some benefit through either medical or surgical treatment.  The most common medications used to treat Paget’s disease are calcitonin, a hormone endogenously produced by humans and animals, and a class of medications called bisphosphonates.   At present, calcitonin is derived from either salmon or humans and is injected under the skin.  Side effects of calcitonin include nausea, a metallic taste, diarrhea, abdominal pain, or allergic reactions.

            Bisphosphonates are a group of medications that can decrease the abnormal bone growth-destruction equilibrium.  The most commonly used bisphosphonate is pamidronate.  Others include alendronate, tiludronate, and risedronate.  Their effectiveness is usually measured by checking levels of alkaline phosphatase in the blood. 

            Acetaminophen and nonsteroidal anti-inflammatory medications such as ibuprofen have been used to treat bone pain associated with Paget’s disease.  Always discuss with your doctor the pros and cons of a medication before taking it.  Exercise to maintain joint range of motion is also very important. 

Authors: Fawad Shaheen, B.A., UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ

               Alex Visco, M.D., New York-Presbyterian Hospital, The University Hospital of Columbia and Cornell, New York, NY