Hereditary multiple exostoses

Last revised by Keshaw Kumar on 23 Feb 2023

Citation, DOI, disclosures and article data

Citation:

Gaillard F, Kumar K, Ranchod A, et al. Hereditary multiple exostoses. Reference article, Radiopaedia.org (Accessed on 30 Mar 2023) https://doi.org/10.53347/rID-1445

DOI:

https://doi.org/10.53347/rID-1445

Permalink:

https://radiopaedia.org/articles/1445?iframe=true

rID:

1445

Article created:

2 May 2008, Frank Gaillard ◉ ◈

Disclosures:

At the time the article was created Frank Gaillard had no recorded disclosures.

View Frank Gaillard's current disclosures

Last revised:

23 Feb 2023, Keshaw Kumar

Disclosures:

At the time the article was last revised Keshaw Kumar had no financial relationships to ineligible companies to disclose.

View Keshaw Kumar's current disclosures

Revisions:

60 times, by 23 contributors - see full revision history and disclosures

Systems:

Musculoskeletal, Paediatrics

Sections:

Syndromes

Synonyms:

Diaphyseal aclasis
Familial osteochondromatosis
Diaphyseal aclasia
Multiple hereditary exostosis
Hereditary multiple exostosis
Multiple hereditary exostoses
HME

Hereditary multiple exostoses/osteochondromas, also known as diaphyseal aclasis, osteochondromatosis, or simply multiple osteochondromas, is an autosomal dominant condition, characterized by the development of multiple osteochondromas.

Hereditary multiple exostoses demonstrate an autosomal dominant inheritance pattern, with incomplete penetrance in females leading to a slightly male predominance. Prevalence is estimated at 1 in 50,000 people ⁶. The number of exostoses, the degree, and type of angular deformity, and even the rate of malignant transformation vary significantly, even within families.

In rare circumstances, hereditary multiple exostoses occurs together with enchondromatosis in a condition known as metachondromatosis.

Diagnosis

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5^th edition) ⁶:

essential: ≥2 radiological osteochondromas at the juxtaepiphyseal region of the long bones and positive family history and/or EXT gene germline mutation

Clinical presentation

Most patients are diagnosed by the age of 5 years, and virtually all are diagnosed by the age of 12 years. Patients may be asymptomatic with a few small lesions or may be significantly deformed by multiple large osteochondromas.

Pathology

Location

Hereditary multiple exostoses can involve any bony in the body except for the calvarium ⁵. Common sites of involvement include the distal femur, proximal tibia, wrist and hands, humerus, ankle, pelvis, and ribs.

Genetics

Hereditary multiple exostoses is thought to result from EXT1, EXT2, or EXT3 gene mutationson chromosomes 8q24 (EXT1), 11p11-13 (EXT2), and 19p (EXT3) ^4,5.

Radiographic features

Except that they are multiple, imaging features are identical to solitary osteochondromas. The skeletal distribution of lesions can significantly vary, with some authors noting that the typical distribution is bilateral and symmetric, whereas others report a strong unilateral predominance.

Often associated with a broadened shaft at the end of long bones, hence the term diaphyseal aclasis.

Treatment and prognosis

Complications

Complications are similar to those of solitary osteochondroma and include:

vascular impingement
neural impingement
fracture
bursitis
deformity and ankylosis
malignant transformation

Malignant transformation is more common than in sporadic cases, with transformation rates reported as high as 25% (lower rates of 3-5% have also been published) ³. The mnemonic GLAD PAST ¹lists the associations with sarcomatous transformation.

Refer to the generic osteochondroma article for more information.