Osteochondroma (Extosis) Symptoms & Causes

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Osteochondromas usually appear near the growth plate, which is located at the ends of long bones (such as the thighbone, upper arm bone or shinbone). Osteochondromas can also occur in the pelvis, spine, or any bone in the body.

Osteochondroma is most common in children and adolescents between 10 and 20 years of age. Osteochondromas normally stop growing when children reach skeletal maturity (when their bones reach their regular adult size).

Can an osteochondroma become cancerous (malignant)?

Very rarely, an osteochondroma can transform into a malignant condition later in adulthood. Your child’s doctor will probably want to keep an eye on the condition for this reason. It is extremely unusual and is therefore not a reason to remove all osteochondromas.


What causes osteochondroma in children?

The cause of osteochondroma is unknown, but the tumor is thought to be related to an abnormality in the growth plate, causing a bony prominence to grow away from the bone.

If a child has several osteochondromas, they are usually the result of a genetic disorder known as multiple hereditary exostoses (MHE) or multiple osteochondromas. However, there is also a non-heredity form of MHE in which multiple osteochondromas occur by chance (sporadically).

Signs and symptoms

What are the symptoms of osteochondroma in children?

In general, osteochondromas are hard masses that grow on top of the bone and only cause pain when nerves, muscles or tendons rub against them.

Keep in mind that each child can experience symptoms of osteochondroma differently, depending on the size and location of the tumor or tumors.

Because the symptoms may also be caused by other, more serious health conditions, it is important to be evaluated by a physician to get an accurate diagnosis. Always consult your child's physician if you have concerns

The following are the most common symptoms of osteochondromas:

   •   A hard, painless mass
          -   The mass can be painful if  nearby muscles or tissues rub over the osteochondroma and become inflamed
   •   Different limb lengths
   •   Shorter than average height for age
   •   Joint and muscle pains

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