Bone Lesions & Conditions

    Hereditary Multiple Exostoses (HME)

    Hereditary condition with multiple exostoses: long-term follow-up and surgical management.

    Medically reviewed: April 2026·Dott. Daniele Priano

    Quick Answers

    What is the risk of malignant tumor in HME?
    The risk of malignant transformation (chondrosarcoma) in hereditary multiple exostoses is higher than in solitary exostosis, estimated between 1% and 5%. This is why regular long-term follow-up is essential, with attention to lesions that grow rapidly, become painful or change appearance in adulthood.
    Will my child inherit the condition?
    HME is inherited in an autosomal dominant pattern: an affected parent has a 50% chance of transmitting the condition to each child. Genetic counseling is available for interested families, and is particularly useful in family planning.
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    Hereditary Multiple Exostoses (HME) is a genetic condition characterized by the appearance of numerous exostoses (osteochondromas) in different skeletal sites, typically near the growth plates of the limbs, pelvis and shoulder girdle. Inheritance is autosomal dominant: an affected parent has a 50% chance of transmitting the condition to each child.

    Unlike solitary exostosis, HME requires a long-term surveillance path, because the issue is not the single lesion but the whole picture: some exostoses can progressively deform the nearby bone, particularly at the forearm (with radio-ulnar dislocation and limited pronation-supination) or the knee, and may sometimes lead to limb length discrepancies. The risk of malignant transformation into chondrosarcoma, although low, is higher than in the solitary form and must be monitored throughout life.

    The approach is that of a multidisciplinary specialist pathway: initial mapping of all lesions, individualized clinical surveillance with imaging targeted to the sites that require it (not automatic periodic total-body X-rays), and shared decisions on which exostoses to treat and in what order. Care is multidisciplinary and team-based — orthopaedics, genetics, radiology, rehabilitation — while Dr. Priano personally handles the clinical assessment, the indication and the operations within his remit as part of this pathway. The goal is not to "remove everything" but to preserve the best possible function with the fewest possible operations, taking advantage of the right window of growth for deformity corrections.

    Assessment and treatment

    When to seek evaluation

    • Family history of multiple exostoses
    • Appearance of multiple bony outgrowths
    • Progressive limb deformities, particularly of the forearm
    • Increasing joint limitations (pronation-supination, knee)
    • Differences in limb length
    • Pain, rapid growth or change of a known lesion

    What is evaluated

    • Complete mapping of lesions
    • Evaluation of secondary deformities (forearm, knee, ankle)
    • Joint function assessment
    • Associated limb length discrepancy
    • Surveillance for malignant transformation

    Treatment options

    • Individualized clinical surveillance, with imaging targeted to the sites that require it
    • Selective excision of symptomatic or at-risk lesions
    • Correction of secondary deformities in the right window of growth
    • Management of associated limb discrepancy

    Frequently Asked Questions

    What is the risk of malignant tumor in HME?▼
    The risk of malignant transformation (chondrosarcoma) in hereditary multiple exostoses is higher than in solitary exostosis, estimated between 1% and 5%. This is why regular long-term follow-up is essential, with attention to lesions that grow rapidly, become painful or change appearance in adulthood.
    Will my child inherit the condition?▼
    HME is inherited in an autosomal dominant pattern: an affected parent has a 50% chance of transmitting the condition to each child. Genetic counseling is available for interested families, and is particularly useful in family planning.
    Does every exostosis need to be removed?▼
    No. In HME we selectively operate only on lesions causing problems: pain, progressive deformities, neurovascular compression or significant functional limitations. The goal is to maintain the best possible function with the minimum number of surgeries over a lifetime.
    When is the right time to correct a forearm deformity?▼
    Forearm deformities are among the most typical of HME and the surgical timing is a delicate decision: operating too early exposes to recurrence with residual growth, too late can make correction more complex. The choice is made case by case based on age, progression and functional impact, taking advantage of the right window of growth.
    Can my child play sports with HME?▼
    In general yes, and physical activity is actually recommended. Some specific advice may be given for exostoses located in sites exposed to direct impact or to compression of nerves and vessels. Sport choice is personalized based on the lesion map and on age.
    How long will follow-up last?▼
    In HME it is useful to **keep a specialist point of reference into adulthood**, adjusting the frequency of checks to the individual risk. In childhood assessments are closer together, to identify evolving deformities and plan surgery in the right windows; in adulthood they become less frequent, remaining oriented to surveillance of the low risk of malignant transformation.

    Important Notice: The information on this page is for educational and informational purposes only and does not constitute medical advice. Each clinical case is unique: the appropriate treatment is determined during the specialist consultation, based on a thorough clinical examination and, where necessary, diagnostic imaging. For any doubts or concerns, please consult a specialist.