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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
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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.[1]

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.[2]
Last updated: 6/27/2011

  1. Hereditary multiple exostoses. Genetics Home Reference. December 2007; Accessed 6/1/2011.
  2. Schmale GA, Wuyts W, Chansky HA, & Raskind WH. Hereditary multiple osteochondromas. GeneReviews. September 2008; Accessed 6/27/2011.