The skeletal system is an important part of the body. It provides the framework for the body, it helps with movements, and it aids in the formation of blood cells. To be able to perform all these functions, the bones need the strength they need, and this comes from the minerals needed such as calcium, vitamin D, and phosphate.
One rare disease of the bones is oncogenic osteomalacia or acquired hypophosphatemic osteomalacia. Oncogenic osteomalacia is a rare tumor-associated condition wherein there is the development of a tumor that causes the bones to become weak and soft. This condition happens when the tumor produces the substance called fibroblast growth factor 23 (FGF23). This growth factor, FGF23, inhibits that ability of the kidneys to absorb phosphate.
More than half of all bone is made from phosphate, and a small percentage are found in the body for tissue and fluid maintenance. Phosphate is vital for keeping the bones strong and healthy. Hence, when there is an impaired ability to absorb phosphate, the bones will become the bones will become brittle, soft and weak.
What happens in oncogenic osteomalacia? The exact etiology or cause of the tumor development linked to oncogenic osteomalacia is still unknown. The disease is diagnosed when the patient manifests clinical features like the presence of the tumor and bone weakening.
The disease starts off with the development of the tumor. The tumor secrets a humoral factor called phosphatonin, that can affect the proximal renal tubules in the kidneys. This is the fibroblast growth factor 23 or FGF23. It inhibits the ability of the kidneys to absorb phosphate.
Also, it reduces the calcitriol production in the kidneys, thus inhibiting phosphate transport. This process leads to increased excretion of phosphate by the kidneys, leading to hypophosphatemia. The end result is the presence of osteomalacia since the bones do not get enough levels of phosphate, which is important for bone strength and health.
As a result, the bones become weak, soft and easily broken.
It has been seen that the clinical and biochemical parameters of oncogenic osteomalacia can become normal if the lesion responsible for the condition is removed.
The initial symptoms of oncogenic osteomalacia include fatigue, bone pain, muscle weakness, frequent fractures, and bone weakness or osteomalacia.
When the doctor recommends testing the blood and urine, the people with oncogenic osteomalacia will have high levels of phosphate in the urine (hyperphosphaturia) and low levels of phosphate in the blood (hypophosphatemia). Aside from these, the patient may also have decreased levels of 1,25-dihydroxy vitamin D in the blood.
The exact reason on why the tumor linked to oncogenic osteomalacia appears is still unclear. However, tumors usually emerge from the abnormal growth of the cells in the body.
As stated earlier, the tumor releases the fibroblast growth factor 23 (FGF23), which is responsible for the regulation of the phosphate and vitamin D levels in the body. This growth factor does this by telling the kidneys how much of these substances to absorb. It also tells the kidneys how much phosphate to excrete in the body through the urine.
Since phosphate is essential for bone health and strength, when there are low levels in the body, the bones become weak and soft. As a result, osteomalacia occurs.
The diagnosis can be made when the patient manifests the signs and symptoms of the disease such as weakness of the bones, soft bones, frequent fractures and decreased levels of phosphate in the blood.
The doctor may conduct a thorough physical assessment and medical history taking to help in diagnosing the condition. These will help rule out other diseases that can cause similar symptoms.
To confirm the levels of phosphate in the blood and urine, the doctor can request a urine test and blood test. When oncogenic osteomalacia is suspected, the doctor can recommend imaging tests to detect the location of the tumor. He can ask for a CT scan or MRI scan. In some cases, he may request for an MR angiography.
The treatment for oncogenic osteomalacia is geared toward the identification of the tumor and the removal of the tumor. It is important to remove all of the tumors to reduce the risk of recurrence. Surgery can be recommended for the tumor excision.
The removal of the tumor may immediately return the levels of phosphate and vitamin D to normal. Usually, the tumors associated with oncogenic osteomalacia are non-cancerous or not malignant. This means that they are unlikely to spread to the other parts of the body.
If the tumor can’t be removed surgically, some doctors recommend taking medicines to increase the levels of vitamin D and phosphate in the body.
Most individuals with oncogenic osteomalacia may fully recover once the tumor has been removed. The doctor must make sure that the tumor has been removed entirely to reduce the risk of recurrence.
Once the tumor has been removed, the levels of phosphate and vitamin D in the blood will return to normal within just days or weeks after the operation. By this time, most patients will feel better, and the symptoms will gradually disappear.
In some cases, however, the tumor can recur and appear in the other parts of the body. Some patients may need frequent MRI or CT scans to see if other tumors will appear or if it will spread to the others parts of the body.
Some patients may also need to take supplements of vitamin D and phosphate, particularly if the tumor is too small to be removed. These supplements will help maintain the normal levels of these substances in the body and to reduce the risk of having soft and weak bones.
For people who had fractures, if the fracture is small and mild, having a cast and therapy is recommended. However, for those with severe ones, they may need surgery and months of therapy to bring back the function of the part of the body. It is then important for patients to be extra careful in their activities. They should avoid contact sports and do unsafe activities that might lead to falls or accidents.