Hereditary multiple osteochondromas (HMO)

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Information for parents about hereditary multiple osteochondromas (previously called hereditary multiple exostoses), a genetic condition that causes growths (bumps) on the bones.

Key points

  • Hereditary multiple osteochondromas (HMO) is a genetic condition where multiple osteochondromas (bony growths) grow on certain bones during childhood and adolescence.
  • Children with suspected HMO should be assessed by a health-care team, which includes an orthopaedic surgeon, geneticist and genetic counsellor.
  • The primary care physician and/or orthopaedic surgeon should monitor the osteochondromas in children with HMO for the possibility of functional limitations and deformities.
  • There is approximately a 2% to 5% lifetime risk for an osteochondroma to become cancerous (chondrosarcoma).
  • Genetic counselling can help families understand HMO, genetic testing and results, the inheritance of the condition and the chances that other children will also be affected.
Last updated: March 6th 2023