The Effects of HME

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Although people with HME may have many exostoses, most are just a nuisance. Usually exostoses only cause a problem when they interfere with something else, such as a joint, nerve or tendon.

Change in Growth Rate

When a bone has an exostosis on it, it tends to grow more slowly than usual. As a result, one of your arms or legs may end up a little shorter than the other. This is not unusual - most people have one leg shorter than the other - but in HME this difference may be more marked. If both legs are affected, you may not be quite as tall as your unaffected brothers or sisters.

The Forearm and Lower Leg

The forearms (between the elbow and wrist) and lower legs (between the knee and ankle) contain two bones. In the forearm these bones are called the ulna and radius, and in the lower leg, the tibia and fibula.

If one of these bones develops an exostosis which slows down its growth, it can cause a problem for the other bone which is growing at the normal rate. For instance, if you have an exostosis on your ulna, the radius may become curved and begin to stick out at the elbow. Similarly, uneven growth of the bones in the lower leg can cause problems at the knee. If this starts happening, it may be possible to lengthen the shorter bone by surgery.

Nerves and Tendons

Sometimes an exostosis grows near a nerve or tendon and can "twang" it when you move. It may need to be removed to stop this.

Pain and Discomfort

Exostoses can be painful, especially when you bump them. They can also cause discomfort by blocking movement at a joint, especially at the elbows and hips.

Also, you may develop a bursa over an exostosis. This is a little slippy bag that develops between a bone and the skin, to prevent friction. Bursas sometimes get inflamed ("bursitis") and this can be the cause of considerable discomfort.

Tumours

An exostosis can very rarely turn into a malignant tumour called a chondrosarcoma. This is usually a slow growing tumour which can often be cured. The warning signs are an increase in size or discomfort after growth has stopped, or unusually rapid growth.

You should always report this sort of change to your doctor.

Although people with HME are more likely to develop a chondrosarcoma than other people, the risk should be kept in proportion. For example, for a female, it's less than the risk that all women face of developing breast cancer.

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