Topic Resources
Paget disease of bone is a
chronic disorder of the skeleton in which areas of bone undergo abnormal
turnover, resulting in areas of enlarged and softened bone.
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The breakdown and formation of bone increase, resulting in bones that are thicker, but weaker, than normal.
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Symptoms may be absent or may include bone pain, bone deformity, arthritis, and painful nerve compression.
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X-rays show the bone abnormalities.
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Pain and complications are treated, and bisphosphonates may be given.
Paget disease can affect any bone, but the most commonly affected bones are the pelvis, thighbone (femur), and skull. The shin (tibia), spine (vertebrae), collarbone (clavicle), and upper arm bone (humerus) are affected less commonly.
Paget disease rarely occurs in people younger than 40. In the
United States, about 1% of people older than 40 have the disorder, and
the prevalence increases with age. However, the prevalence of the
disease seems to be decreasing. Men are 50% more likely than women to
develop it. Paget disease is more common in Europe (excluding
Scandinavia), Australia, and New Zealand.
Causes
Normally, cells that break down old bone (osteoclasts) and cells
that form new bone (osteoblasts) work in balance to maintain bone
structure and integrity. In Paget disease, both osteoclasts and
osteoblasts become overactive in some areas of bone, and the rate at
which bone is broken down and rebuilt (called bone remodeling)
in these areas increases tremendously. The overactive areas enlarge
but, despite being large, are structurally abnormal and weak.
The cause of Paget disease is unknown in most people. The
disorder tends to run in families. Specific, identified gene
abnormalities contribute in about 10% of people who have Paget disease,
and other genetic abnormalities probably contribute in others. Also,
some evidence suggests that a virus is involved. However, there is no
evidence that the disorder is contagious.
Complications
The most common complication of Paget disease of bone is
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Osteoarthritis (a joint disorder)
Osteoarthritis develops in up to 50% of people and may develop in joints near the involved bone.
Fractures tend to occur more easily than normal at involved bones
because these bones are weakened by Paget disease. Such fractures are
called pathologic fractures.
Overgrown bone may compress nerves and other structures passing
through small openings. The spinal canal may become narrow and compress
the spinal cord.
Rarely, heart failure
develops because the increased blood flow through the affected bone
puts extra stress on the heart. Because blood flow through affected
bones is unusually high, those bones may bleed excessively during
surgery. The affected bone becomes cancerous in up to 1% of people who
have Paget disease. People whose disease progresses to bone cancer
usually develop an osteosarcoma (a cancerous bone tumor).
High blood levels of calcium (hypercalcemia) may very rarely occur in bedridden people with Paget disease.
Symptoms
Paget disease usually causes no symptoms. However, bone pain,
bone enlargement, or bone deformity may occur. Bone pain may be deep,
aching, and occasionally severe and may worsen at night. The enlarging
bones may compress nerves, causing more pain. If osteoarthritis occurs,
joints become painful and stiff.
Other symptoms vary depending on which bones are affected.
The skull may enlarge, and the brow and forehead may look more
prominent (called frontal bossing). A person may notice this enlargement
when a larger hat is needed. Enlarged skull bones may damage the inner
ear (cochlea), which can cause hearing loss, and dizziness. The enlarged
skull bones can compress nerves, which causes headaches. The veins on
the scalp may bulge, possibly because of the increased blood flow
through the skull bones.
Forehead Enlargement in Paget Disease
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Bones the upper arm, thigh, or calf may appear bowed and are more
likely to break because the bone is weakened by Paget disease. The
vertebrae may enlarge, collapse, or both because bones affected by Paget
disease are weak. Weakened vertebrae could result in a loss of height, a
hunched posture, or pinching of the nerves of the spinal cord, causing
pain, numbness, or weakness.
Bowing of the Shinbone in Paget Disease
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Diagnosis
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X-rays
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Blood tests
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Bone scan
Paget disease is often discovered accidentally when x-rays or
laboratory tests are done for other reasons. Otherwise, the diagnosis of
Paget disease may be suspected based on the symptoms and a physical
examination.
The diagnosis of Paget disease of bone can be confirmed by x-rays
showing abnormalities characteristic of Paget disease and by a
laboratory test to determine blood levels of alkaline phosphatase (an
enzyme involved in bone formation), calcium, and phosphate.
A bone scan (a radionuclide scan using technetium) shows which bones are affected.
Prognosis
The prognosis for people with Paget disease is most often very
good. However, the few people who develop bone cancer have a poor
prognosis. People who develop other rare complications, such as heart
failure or compression of the spinal cord, may also have a poor
prognosis, unless treatment of these complications is timely and
successful.
Treatment
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Treatment of pain and complications
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Bisphosphonates
A person who has Paget disease needs treatment if the symptoms
cause discomfort or if there is a significant risk or suggestion of
complications, such as hearing loss, osteoarthritis, and deformity.
People who do not have symptoms may not need any treatment.
Commonly used pain relievers (analgesics) such as acetaminophen
and nonsteroidal anti-inflammatory drugs (NSAIDs) help reduce bone
pain. If one leg becomes bowed and shortened, heel lifts can help make
walking easier. Sometimes surgery is needed to relieve pinched nerves or
to replace a joint that has become arthritic from Paget disease.
Bisphosphonates are drugs that inhibit bone turnover. One of several bisphosphonates—alendronate, etidronate, pamidronate, risedronate, tiludronate, or zoledronate—can be used to slow the progression of Paget disease. Except for pamidronate
and zoledronate, which are usually given by vein (intravenously), these
drugs are given by mouth. These drugs are given for the following:
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Before orthopedic surgery to prevent or reduce bleeding during surgery
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To treat bone pain caused by Paget disease
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To prevent or slow the progression of complications (such as hearing loss, bone deformity, arthritis, weakness, or paralysis), especially in people who cannot have surgery
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To people with a blood level of alkaline phosphatase twice the normal level or higher
Calcitonin is
occasionally injected under the skin or into muscle. It is not as
effective as the bisphosphonates and is used only when the other drugs
cannot be given. Denosumab may be another alternative for people who cannot take bisphosphonates.
Doctors encourage weight bearing (such as standing and walking).
Excessive bed rest (except for sleeping at night) should be avoided, if
possible, to prevent hypercalcemia.
Because bone is being remodeled rapidly, people should consume adequate amounts of calcium and vitamin D
in their diet. Vitamin D helps the body absorb calcium and add it to
bone (a process called bone mineralization). Vitamin D and calcium
supplements are often needed. Otherwise, poor bone mineralization and
bone weakening (osteomalacia) may occur.
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