Hereditary Multiple Exostoses
by Shannan
Hereditary multiple exostoses is an inherited disorder affecting bone growth.  This disorder is passed from the genes of the affected parent to their children.  The disorder is autosomal dominant, so if one parent has hereditary multiple exostoses then the chances are fifty percent that any child can develop hereditary multiple exostoses throughout the course of their life (“Exostoses, Multiple, Type II”).  Occasionally a patient will develop hereditary multiple exostoses with no family history of the disorder, in this case it is referred to as a spontaneous mutation (“Exostoses, Multiple, Type II”).  There are four chromosomes that the defect occurs on, they are chromosomes 1, 8, 11, and 19 (“Genetic Studies”).  There is some evidence that there may be different genes at these locations but it is not certain.  Patients with hereditary multiple exostoses may have difficulty walking or using arms in this case the exostoses can be removed to ease the pain and discomfort.

Hereditary multiple exostoses is a rare familial dyschondroplastic disease in which bony protuberances form on the shafts of the long bones and eventually develop into caps of cartilage covering the ends of  bones.  The affected joints lose their mobility, and the bones stop growing.  The disease begins in childhood and has no cure.  Very rarely a chondrosarcoma may develop from the cap of the exostoses. (Anderson, K., 1998, p755) Hereditary multiple exostoses can cause a variety of problems.  The exostoses usually grow near the growth center of the bone causing pain and discomfort.  These abnormal bone growth are found most frequently at the ends of long bones, scapula and sometimes the ribs (“Exostoses, Multiple, Type II”).  The exostoses may cause deformity of limbs such as shorten range of motion due to exostoses in elbows and knees (“Exostoses,Multiple, Type II”).  Patients with hereditary multiple exostoses  have an increased risk for osteosarcoma.  They may have reduced stature and nerve compression.  Patients with hereditary multiple exostoses may also suffer from urinary or intestinal tract obstruction (“Exostoses, Multiple, Type II”).  When nerve compression occurs there are two options the patients can choose between to relieve the pain and discomfort; nerve block and/or removal of exostoses.  Hereditary multiple exostoses is more severe in males than in females.  Exostoses can appear on spine and skull but it is very rare.

Genetic studies are still being done in order to provide a better diagnosis.  Affected families can now be screened for hereditary multiple exostoses.  The test used screen for hereditary multiple exostoses can be very useful in testing children who may be mildly affected, however the test are still in the research stage.  Physicians should be able to offer the test in the near future.  The genetic studies being done are important because the disease varies from person to person.  Some people develop lots of lumps while others develop only one or two lumps.  A lump appears when one gene stops working (“Genetic Studies”).  The exostoses usually only affect certain bones because the patient usually only gets the defected chromosome from one parent and not both (“Genetic Studies”).  There is currently no prevention or cure but a greater understanding of what causes lumps may lead to a way of preventing the lumps from developing.  The outlook for patients with hereditary multiple exostoses is much more hopeful than it was only a few years ago.   There are few medical interventions available for hereditary multiple exostoses
patients ranging from a variety of drugs to surgical removal of the exostoses.  The most common intervention used to eliminate the pain caused by the exostoses is having them surgically removed.  This procedure is performed if the lumps become noticeable or get in the way, if they are blocking normal movement, pressing on a nerve or tendon, causing uneven growth, causing pain and discomfort and to prevent the exostoses from becoming malignant (“Treatment of Hereditary Multiple Exostoses”).  Although malignancy rarely occurs it is a problem hereditary multiple exostoses patients have to be aware of (“Multiple Hereditary Exostoses”).  The risk of malignant change is 1.3% in those over 21 (“Exostoses, Multiple, Type I”).  In patients with multiple exostoses 20-50% of them experience malignant change (“Exostoses, Multiple, Type I”).  The upper end of the femur and the pelvis were the main locations this occurred (“Exostoses, Multiple, Type I”).  If an exostoses becomes malignant it must be removed (“Multiple Hereditary Exostoses”). Having the exostoses removed is a fairly simple procedure which can sometimes be done in outpatient surgery.  Sometimes just having the exostoses removed is not enough to straighten the bone back out after bowing has occurred (“Multiple Hereditary Exostoses”).  Therefore the bone must be straightened by either cutting the bone and
holding it in place while it heals or if the child is still growing the bone can straightened by changing the growth rate on one side of the bone (“Multiple Hereditary Exostoses”). After the exostoses is removed there is a 50% percent chance that it will grow back.  If and when it reappears chances are it won’t be as bad.

Although surgically removing the exostoses has its advantages it also has its disadvantages.  In some instances some very rare complications can occur.  The exostoses may somehow stretch due to the pressure of the surgery or post-surgical swelling causing entrapment of a nearby nerve (Dr. Evan Collins, personal communication, March 3, 2000). In this instance the patient is introduced to new medical problems, such as peroneal nerve palsy as well as reflex sympathetic dystrophy syndrome (Dr. Evan Collins, personal communication, March 3, 2000).  So now what was supposed to be a simple surgical procedure has now been stretched into months of pain and physical therapy.  If necessary another surgical procedure can be done to remove the exostoses that is compressing the nerve (Dr. Evan Collins, personal communication, March 3, 2000).

Hereditary multiple exostoses is a rare disease.  Some patients with hereditary multiple exostoses can live normal lives without any discomfort while others suffer a great deal.  Currently there is not a lot they can do for patients with hereditary multiple exostoses other than monitor its progression.  However if the exostoses present a problem such as cause pain or prevent movement they can be surgically removed.  Researchers are still researching hereditary multiple exostoses in hopes to better understand how it is caused so they can provide better treatments and hopefully one day prevent hereditary multiple exostoses altogether.
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