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Genetic and Rare Diseases Information Center (GARD)

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Hereditary multiple osteochondromas


Other Names for this Disease

  • Hereditary multiple exostoses
  • Hereditary multiple exostosis
  • HMO
  • Multiple exostoses
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Overview

What is hereditary multiple osteochondromas?

How is hereditary multiple osteochondromas inherited?

Is genetic testing available for hereditary multiple osteochondromas?

What is hereditary multiple osteochondromas?

Hereditary multiple osteochondromas (HMO) (formerly called hereditary multiple exostoses) is a genetic condition in which people develop multiple benign (noncancerous) bone tumors that are covered by cartilage (called osteochondromas). The number and location of osteochondromas varies greatly among affected individuals. These tumors are not present at birth, but almost all affected people develop multiple osteochondromas by the time they are 12 years old. Once the bones stop growing, the development of new osteochondromas also usually stops. Osteochondromas can cause abnormal growth of the arms, hands, and legs, which can lead to uneven limb lengths (limb length discrepancy) and short stature. These tumors may cause pain, limit joint movement, and exert pressure on nerves, blood vessels, and surrounding tissues. Osteochondromas are typically benign; however, researchers estimate that people with HMO have about a 1% lifetime risk of these tumors becoming a cancerous osteochondrosarcoma. HMO is caused by mutations in the EXT1 and EXT2 genes and is inherited in an autosomal dominant pattern.[1]
Last updated: 6/1/2011

How is hereditary multiple osteochondromas inherited?

HMO is caused by mutations in the EXT1 and EXT2 genes. It is inherited in an autosomal dominant pattern, which means that one copy of the altered gene in each cell is sufficient to cause this condition. In most cases, an affected individual inherits the mutation from one affected parent. Other cases result from new mutations in the gene and occur in people with no history of the condition in their family.[2]

Most affected individuals (96%) that have inherited a gene mutation from their parent show signs and symptoms of this condition. However, the family history may appear negative because of the failure to recognize the disorder in family members and/or reduced penetrance. Reports have suggested that some females may not show clinical features of HMO but still have the gene mutation that causes this condition.[1]
Last updated: 6/27/2011

Is genetic testing available for hereditary multiple osteochondromas?

GeneTests lists the names of laboratories that are performing genetic testing for hereditary multiple osteochondromas. To view the contact information for the clinical laboratories conducting testing for the EXT1 gene, click here.  To view the contact information for the clinical laboratories conducting testing for the EXT2 gene, click here.

Please note:  Most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional.  Below, we provide a list of online resources that can assist you in locating a genetics professional near you.
Last updated: 6/1/2011

References
  1. Schmale GA, Wuyts W, Chansky HA, & Raskind WH. Hereditary multiple osteochondromas. GeneReviews. September 2008; http://www.ncbi.nlm.nih.gov/books/NBK1235. Accessed 6/27/2011.
  2. Hereditary multiple exostoses. Genetics Home Reference. December 2007; http://ghr.nlm.nih.gov/condition/hereditary-multiple-exostoses. Accessed 6/1/2011.


Other Names for this Disease
  • Hereditary multiple exostoses
  • Hereditary multiple exostosis
  • HMO
  • Multiple exostoses
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.