Hereditary multiple exostoses demonstrates an autosomal dominant inheritance pattern, with incomplete penetrance in females. The number of exostoses, the degree and type of angular deformity, and even the rate of malignant transformation vary significantly, even within families.
Most patients are diagnosed by the age of 5 years, and virtually all are diagnosed by the age 12 years. Patients may be asymptomatic with a few small lesions or may be significantly deformed by multiple large osteochondromas.
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.
Are also similar or those of solitary osteochondroma and include
- vascular impingement
- neural impingement
- 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 generic osteochondroma article for more information.
The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.
- bone-forming tumours
- cartilage-forming tumours
- chondromyxoid fibroma
- fibrous bone lesions
- bone marrow tumours
- other bone tumours or tumour-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumour of bone
- Gorham massive osteolysis
- haemophilic pseudotumour
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal haemangiopericytoma
- primary intraosseous haemangioma
- simple bone cyst
- impending fracture risk
- 1. Dähnert W. Radiology review manual. Lippincott Williams & Wilkins. (2007) ISBN:0781738954. Read it at Google Books - Find it at Amazon
- 2. Eisenberg RL, Johnson NM. Comprehensive radiographic pathology. Mosby Inc. (2007) ISBN:0323036244. Read it at Google Books - Find it at Amazon
- 3. Murphey MD, Choi JJ, Kransdorf MJ et-al. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation. Radiographics. 20 (5): 1407-34. Radiographics (full text) - Pubmed citation