Paget's Bone Disease
Does Paget's disease have a cure? All the information on this bone disorder and its prognosis.
Symptoms and Causes
Paget's bone disease, or osteitis deformans, is a chronic disorder characterized by an abnormally rapid and uncontrolled process of bone remodeling or turnover. Bone remodeling is the mechanism through which new bone tissue slowly replaces old bone tissue. In Paget's disease, bone is rebuilt at a much faster rate than normal, resulting in bones that are too large or fragile and may become deformed.
The disease can affect any bone, with the pelvis, skull, femur, and spine being the most commonly affected. Based on the number of bones that develop Paget's disease, it is classified as:
- Monostotic Paget's disease: affects a single bone.
- Polyostotic Paget's disease: appears in several bones.
After osteoporosis, Paget's disease is the most common bone disorder in the Western world.
Symptoms
In many cases, Paget's disease does not show symptoms. When symptoms do appear, they may include the following:
- Bone pain: caused by the enlargement of the bone and the formation of microfractures due to its fragility.
- Swelling or deformity of the bones: bones in the legs or arms appear curved. In the case of the legs, the deformity may result in a limp due to the size difference between the bones. The skull may enlarge, and if the spine is affected, it may cause a hump.
- Increased temperature in the skin over the affected bone: due to the high bone vascularization (increase in the number of blood vessels) caused by the disease, accompanied by skin vascularization.
- Joint pain: deformed bones may exert additional pressure on adjacent joints, wearing down the cartilage.
Causes
Paget's disease results from an imbalance in the function of osteoclasts, the cells that destroy or reabsorb old bone, and osteoblasts, the cells that form new bone. Both types of cells become hyperactive, significantly increasing the rate of bone remodeling.
The cause of this imbalance is unknown, although it is thought to have a genetic component: mutations in the SQTM1, TNFRSF11a, and TNFRSF11b genes have been identified, leading to an increase in osteoclast formation and activity. Additionally, some authors have linked Paget's disease to viral infections from paramyxoviruses, such as measles, rubella, or varicella-zoster, as nuclear inclusions have been observed in diseased osteoclasts similar to those found in cells infected by paramyxoviruses. However, this is a controversial theory with no consensus.
Risk Factors
The risk of developing Paget's disease increases under the following conditions:
- Family history.
- Age over 50.
- Male sex.
Complications
One of the most frequent complications is osteoarthritis, caused by the excessive pressure exerted by deformed bones on adjacent joints. Hearing loss is also common when the disease affects the skull, specifically the ossicles of the inner ear. Additionally, if the spine is involved, it may end up compressing the nerve roots of the spinal cord, causing neurological symptoms such as numbness, tingling, or weakness in the limbs.
In more advanced cases of the disease, the increased vascularization of the affected bones increases blood flow, leading to increased cardiac output, which, in some cases, can result in heart failure. Moreover, in rare cases, the affected bones can transform into an osteosarcoma, which typically has a poor prognosis since surgery is often unsuccessful, and osteosarcomas arising from Paget's disease rarely respond to chemotherapy.
Prevention
As it is a disease of unknown cause and mainly genetic risk factors, no ways to prevent its onset have been described.
What doctor treats Paget's disease?
Paget's bone disease is evaluated and treated in the rheumatology unit.
Diagnosis
To confirm Paget's bone disease, the following tests are performed:
- Blood test: usually shows elevated levels of the enzyme alkaline phosphatase. In asymptomatic cases, this is often the first sign, typically detected accidentally during routine blood tests or tests ordered for other reasons.
- X-ray: X-ray images of the bones allow for the identification of Paget’s disease characteristic anomalies, such as fractures, bone enlargement, or deformities.
- Bone scintigraphy: measures the level of bone involvement. A radionuclide emitting gamma radiation is injected into the patient, and images are taken using a gamma camera. The most affected bone areas absorb more radionuclide and will appear darker in the image.
Treatment
The goal of Paget's disease treatment is to prevent or delay potential complications and slow the progression of the disease, although the damage caused is irreversible. Different approaches exist based on its severity:
- Conservative treatment:
- Pain relievers or non-steroidal anti-inflammatory drugs (NSAIDs) to alleviate bone pain.
- Orthotic devices, such as canes or orthopedic shoes, to correct and improve gait.
- Physiotherapy: specific exercises to maintain joint mobility and bone strength.
- Diet rich in calcium and vitamin D. Supplements may also be taken.
- Pharmacological treatment:
- Anti-resorptive medications (bisphosphonates or aminobisphosphonates): inhibit osteoclast activity, regulating the bone remodeling process.
- Synthetic salmon calcitonin, for patients who cannot tolerate or do not respond to anti-resorptive drugs.
- Surgical treatment: in more advanced cases, surgery may be necessary.
- Radicular decompression: release of a nerve compressed by bone growth.
- Prosthetic surgery: in cases of severe osteoarthritis, joint replacement may be required.
- Bone realignment, in cases of severely deformed bones.
