Oncogenic osteomalacia

What causes oncogenic osteomalacia?

Tumor-induced osteomalacia is caused by the development of a tumor that releases fibroblast growth factor 23 (FGF23). FGF23 is responsible for regulating levels of phosphate and vitamin D in the body by telling the kidneys how much phosphate to absorb and how much phosphate to release from the body in the urine. When there is too much FGF23 in the body, the kidneys are not able to absorb the appropriate amount of phosphate. This means that too much phosphate is released from the body in the urine. Phosphate is important for keeping bones strong and healthy. Therefore, when there is not enough phosphate for the bones, they begin to soften and weaken, causing osteomalacia.

Exactly what causes the development of the tumors associated with tumor- induced osteomalacia is unknown. It is most likely that these tumors develop by chance.

Last updated on 05-01-20

How is oncogenic osteomalacia diagnosed?

Oncogenic osteomalacia is diagnosed when an individual has signs and symptoms consistent with the disease such as fractures, bone weakening, and low levels of phosphate in the blood (hypophosphatemia). A doctor should rule out other causes of these symptoms. Doctors can confirm that the low levels of phosphate in the blood are due to the kidneys being unable to absorb phosphate. This can be done by comparing the levels of phosphate in the blood to that in the urine. In some cases, people with oncogenic osteomalacia may be misdiagnosed as having other disorders such as rheumatic disorders or psychiatric disorders. A misdiagnosis can occur because oncogenic osteomalacia is very rare.

When oncogenic osteomalacia is suspected, the tumor that is causing the disease must be detected in order to confirm the diagnosis and plan a surgery to remove the tumor. A number of imaging techniques can be used to find the tumor including CT scan, MRI, and MR angiography. In many cases, the tumor is too small to be detected using imaging of the whole body, so other kinds of imaging tests may be necessary. In some cases, it may be necessary to sample levels of FGF23 in multiple blood vessels throughout the body. Parts of the body where FGF23 levels are the highest are more likely to be closer to the tumor.

Last updated on 05-01-20

Is oncogenic osteomalacia inherited?

We were not able to find any reports of more than one person being affected with oncogenic osteomalacia in a family. Therefore, it is not thought that family members of an affected individual are at any increased risk of developing the disease themselves. It is most likely that the disease occurs by chance and does not run in families.

Last updated on 05-01-20

What is the long-term outlook for people affected with oncogenic osteomalacia?

Most people affected by oncogenic osteomalacia have a full recovery when the tumor that is causing the disease is removed. The levels of phosphate and vitamin D in the blood typically return to normal levels within a few days or a week after the surgery. Most affected individuals start to feel better at this time, and the bones continue to strengthen for up to a year after surgery. In rare cases, the tumor that causes oncogenic osteomalacia may recur in the same place or spread to other parts of the body. Therefore, it is important that people with this disease receive frequent imaging of the body, even after the tumor is removed.

For some people with oncogenic osteomalacia, the tumor that is causing the disease cannot be found because it is so small. For these people, medications that control the levels of phosphate in the blood may help to relieve symptoms. However, it is possible that the medications could cause side effects such as kidney problems. Imaging and other tests should occur at least once a year in order to see if improved technology can help health care providers find the tumor.

Last updated on 05-01-20

How might oncogenic osteomalacia be treated?

Treatment for oncogenic osteomalacia is focused on identifying and removing the tumor that is causing the disease. It is important that all of the tumor is removed to reduce the changes that it will come back again. For most people, removing the tumor cures symptoms of the disease because levels of phosphate and vitamin D are returned to normal. Improvement of symptoms typically occurs within the first weeks or months of surgery.

Typically, the tumors associated with oncogenic osteomalacia are not malignant, meaning that they are unlikely to spread to other parts of the body. Therefore, chemotherapy and radiation therapy are not widely used to treat patients with this disease. After the tumor is removed, it is important that affected individuals continue to receive frequent monitoring to make sure that the tumor does not grow back. This monitoring can take place with frequent imaging and testing levels of FGF23 in the blood.

When the tumor cannot be located or cannot be removed surgically, medications are available that can help increase the levels of phosphate and vitamin D in the blood. This is possible by taking phosphate supplements and calcitriol, which helps increase levels of vitamin D.

Last updated on 05-01-20


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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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