Hereditary multiple osteochondromas

How is hereditary multiple osteochondromas inherited?

Inheritance of HMO is autosomal dominant, which means that having a mutation in one copy of a gene responsible for HMO is sufficient to cause a person to develop HMO. In most cases, a person with HMO inherits the mutation from a parent with HMO. Other cases may result from a new mutation in the gene, occurring in people with no family history of HMO. About 96% of females with a mutation responsible for HMO will develop osteochondromas (a phenomenon known as reduced penetrance), and 100% of males will develop osteochondromas. It is not known why some females with a mutation responsible for HMO do not develop signs and symptoms.

Last updated on 05-01-20

What is the risk of malignant transformation in hereditary multiple exostoses?

Although the estimated risk of malignant transformation in HME has varied within studies, the majority of researchers agree the lifetime risk is between 1-2%.

The average age for a malignant transformation to occur is between 28-35 years old. Malignant transformation is very rare in children, but the risk increases with age, especially after the age of 30.

In 2011, a group of researchers tried to find risk factors which might indicate individuals with HME at a greater risk for developing chondrosarcomas (the cancerous form of osteochondromas). The study looked at gender, number of exostoses, genetic disposition and type of mutation. None of the factors were found to correlate with an increased or decreased risk of malignant transformation.

Last updated on 05-01-20

How might a malignant transformation in hereditary multiple exostoses (HME) be treated?

Chondrosarcomas in a person with HME tend to be well differentiated and low grade tumors. The tumors usually grow slowly and do not readily metastasize. Surgical removal is the recommended treatment as the condrosarcomas do not respond to radiation or chemotherapy.

The prognosis or long term outlook after surgical removal of the chondrosarcoma for a person with HME is good as long as the tumor has not metastasized.

Last updated on 05-01-20

How might malignant transformation in hereditary multiple exostoses (HME) be diagnosed?

Surface irregularities and unorganized chalk deposits with light areas in the middle of the tumor and cartilage cap may be seen on a bone scan, ultrasound or preferably an MRI. However the diagnosis of chondrosarcoma can only be confirmed by a bone biopsy.

Last updated on 05-01-20

Is screening recommended for malignant transformation in hereditary multiple exostoses (HME)?

At present, medical researchers agree that more studies need to be performed to determine the best screening protocols for those with HME, including the study of benefit/cost/risk.

However a compelling study was published in 2014 by Czajka and DiCaprio which compares the screening of malignant transformation in people with HME to the screening of breast and cervical cancer in women. The authors conclude that screening should be offered to individuals with HME over the age of 16 (or when bone growth has been completed). They propose screening should include a thorough clinical examination and a full body MRI every two years. If an MRI is not possible than a bone scan be performed, followed by an ultrasound of the cartilage cap of any suspicious findings.

The Czajka and DiCaprio further recommend that individuals with HME should be made aware of warning signs of malignant transformation and taught self examination techniques.

Last updated on 05-01-20

What are the signs and symptoms of malignant transformation in hereditary multiple exostoses (HME)?

A doctor may become suspicious of a malignant transformation if there is an increase in the size of the tumor in adults when bone growth is already complete. In addition, cancer should be suspected if the thickness of the cartilaginous cap of the osteochondroma is over 1-2 centimeters (normally, after bone growth is complete, the cap is only a few millimeters thick).

Other signs of a malignant transformation may include bone pain, temporary loss of sensory or motor function due to compression of a nerve (neurapraxia) or pressure related symptoms in nearby organs.

Last updated on 05-01-20

Social Networking Websites

MHE Reseach Foundation Facebook

Visit the MHE Research Foundation on Facebook.

Last updated on 04-27-20

Name: MHE Research Foundation 8019 Harbor View Terrace
Brooklyn, NY, 11209, United States
Phone: 917-848-7774 Email: Url:
Name: MHE Coalition Phone: 845-258-6058 Email: Url:
Name: MHE and Me- A Support Group for Kids with Multiple Hereditary Exostoses PO Box 651
Pine Island, NY, 10969-0651,
Phone: 845-258-6058 Email: Url:

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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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