Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.


Genetic and Rare Diseases Information Center (GARD)

Print friendly version

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.


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


  1. Schmale GA, Wuyts W, Chansky HA, & Raskind WH. Hereditary multiple osteochondromas. GeneReviews. September 2008; Accessed 6/27/2011.
Your Questions Answered
by the Genetic and Rare Diseases Information Center

2 question(s) from the public on Hereditary multiple osteochondromas have been answered. See questions and answers. You can also submit a new question.

Basic Information

  • Genetics Home Reference (GHR) contains information on Hereditary multiple osteochondromas. This website is maintained by the National Library of Medicine.
  • The National Organization for Rare Disorders (NORD) is a federation of more than 130 nonprofit voluntary health organizations serving people with rare disorders. Click on the link to view information on this topic.

In Depth Information

  • Medscape Reference provides information on this topic. Click on the link to view this information. You may need to register to view the medical textbook, but registration is free.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs.  Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Hereditary multiple osteochondromas. Click on the link to view a sample search on this topic.