Hereditary multiple exostoses
Updates to Article Attributes
Hereditary multiple exostoses/osteochondromas, also known as diaphyseal aclasis, osteochondromatosis, or simply multiple osteochondromas is an autosomal dominant condition, characterised by the development of multiple osteochondromas.
Epidemiology
Hereditary multiple exostoses demonstrate an autosomal dominant inheritance pattern, with incomplete penetrance in females leading to a slightly male predominance. Prevalence is estimated in 1 in 50,000 people 6. The number of exostoses, the degree, and type of angular deformity, and even the rate of malignant transformation varies significantly, even within families.
Diagnosis
Diagnostic criteria according to the WHO classification of soft tissue and bone tumours (5th 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.
Complications
Are also 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 1 lists the associations with sarcomatous transformation.
Refer to the generic osteochondroma article for more information.
See also
-<p><strong>Hereditary multiple exostoses/osteochondromas</strong>, also known as <strong>diaphyseal aclasis</strong>, <strong>osteochondromatosis</strong>, or simply <strong>multiple osteochondromas </strong>is an <a href="/articles/autosomal-dominant">autosomal dominant</a> condition, characterised by the development of multiple <a href="/articles/osteochondroma">osteochondromas</a>.</p><h4>Epidemiology</h4><p>Hereditary multiple exostoses demonstrate an autosomal dominant inheritance pattern, with incomplete penetrance in females leading to a slightly male predominance. Prevalence is estimated in 1 in 50,000 people <sup>6</sup>. The number of exostoses, the degree, and type of angular deformity, and even the rate of malignant transformation varies significantly, even within families.</p><h4>Diagnosis</h4><p>Diagnostic criteria according to the <a href="/articles/who-classification-of-tumors-of-soft-tissue">WHO classification of soft tissue and bone tumours (5th edition)</a> <sup>6</sup>:</p><ul><li>essential: ≥2 radiological osteochondromas at the juxtaepiphyseal region of the long bones and positive family history and/or <em>EXT</em> gene germline mutation</li></ul><h4>Clinical presentation</h4><p>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. </p><h4>Pathology</h4><h5>Location</h5><p>Hereditary multiple exostoses can involve any bony in the body except for the calvarium <sup>5</sup>. Common sites of involvement include the distal femur, proximal tibia, wrist and hands, humerus, ankle, pelvis, and ribs.</p><h5>Genetics</h5><p>Hereditary multiple exostoses is thought to result from <em>EXT1</em>, <em>EXT2</em>, or <em>EXT3</em> gene mutations<sup> </sup>on chromosomes 8q24 (<em>EXT1</em>), 11p11-13 (<em>EXT2</em>), and 19p (<em>EXT3</em>) <sup>4,5</sup>.</p><h4>Radiographic features</h4><p>Except that they are multiple, imaging features are identical to solitary <a href="/articles/osteochondroma">osteochondromas</a>. 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.</p><p>Often associated with a broadened shaft at the end of long bones, hence the term diaphyseal aclasis. </p><h4>Complications</h4><p>Are also similar to those of solitary <a href="/articles/osteochondroma">osteochondroma</a> and include:</p><ul>-<li>vascular impingement</li>-<li>neural impingement</li>-<li>fracture</li>-<li><a href="/articles/bursitis">bursitis</a></li>-<li>deformity and ankylosis</li>-<li>malignant transformation</li>- +<p><strong>Hereditary multiple exostoses/osteochondromas</strong>, also known as <strong>diaphyseal aclasis</strong>, <strong>osteochondromatosis</strong>, or simply <strong>multiple osteochondromas </strong>is an <a href="/articles/autosomal-dominant">autosomal dominant</a> condition, characterised by the development of multiple <a href="/articles/osteochondroma">osteochondromas</a>.</p><h4>Epidemiology</h4><p>Hereditary multiple exostoses demonstrate an autosomal dominant inheritance pattern, with incomplete penetrance in females leading to a slightly male predominance. Prevalence is estimated in 1 in 50,000 people <sup>6</sup>. The number of exostoses, the degree, and type of angular deformity, and even the rate of malignant transformation varies significantly, even within families.</p><h4>Diagnosis</h4><p>Diagnostic criteria according to the <a href="/articles/who-classification-of-tumors-of-soft-tissue">WHO classification of soft tissue and bone tumours (5th edition)</a> <sup>6</sup>:</p><ul><li>essential: ≥2 radiological osteochondromas at the juxtaepiphyseal region of the long bones and positive family history and/or <em>EXT</em> gene germline mutation</li></ul><h4>Clinical presentation</h4><p>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. </p><h4>Pathology</h4><h5>Location</h5><p>Hereditary multiple exostoses can involve any bony in the body except for the calvarium <sup>5</sup>. Common sites of involvement include the distal femur, proximal tibia, wrist and hands, humerus, ankle, pelvis, and ribs.</p><h5>Genetics</h5><p>Hereditary multiple exostoses is thought to result from <em>EXT1</em>, <em>EXT2</em>, or <em>EXT3</em> gene mutations<sup> </sup>on chromosomes 8q24 (<em>EXT1</em>), 11p11-13 (<em>EXT2</em>), and 19p (<em>EXT3</em>) <sup>4,5</sup>.</p><h4>Radiographic features</h4><p>Except that they are multiple, imaging features are identical to solitary <a href="/articles/osteochondroma">osteochondromas</a>. 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.</p><p>Often associated with a broadened shaft at the end of long bones, hence the term diaphyseal aclasis. </p><h4>Complications</h4><p>Are also similar to those of solitary <a href="/articles/osteochondroma">osteochondroma</a> and include:</p><ul>
- +<li>vascular impingement</li>
- +<li>neural impingement</li>
- +<li>fracture</li>
- +<li><a href="/articles/bursitis">bursitis</a></li>
- +<li>deformity and ankylosis</li>
- +<li>malignant transformation</li>
Image 31 X-ray (Frontal) ( create )
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