HEREDITARY MULTIPLE EXOSTOSIS

The above pictures are of a 6 year old boy who presented with painless lumps in many sites of the body.

Upon X-Ray evaluation it was confirmed to be a case of Hereditary Multiple Exostosis

DISCUSSION :

Definition

Developmental osseous anomaly resulting in exophytic outgrowth on surface of bone

Radiography Findings:

0 Cartilage covered bony projection (exostosis) on external surface of bone

Calcification of hyaline cartilage cap

o Pedunculated type: slender pedicle directed away from joint.

Lesion grows at right angles to long axis of host bone

o Sessile type: Broad-based attachment to cortex

o Undertubulation of long bones (Erlenmeyer flask deformity)

o When to suspect Malignant Degeneration :

Clinical: 30 years of age ; Pelvis, Shoulder affected ; Multiple in number ;

Increasing pain and mass at the site of known osteochondroma

Radiologic : Development of thick, bulky, cartilaginous cap ( thickness > 2cm-adults; > 3 cms-children)

Dispersed calcifications within cartilaginous cap

Bone destruction

Development of soft tissue mass

Altered appearance on sequential studies

Clinical Features

Most common signs/symptoms: Usually painless mass, present for many years

Painful with impingement on nerves/blood vessels

Bursa can form over cap

Pain in absence of fracture, nerve compression, or bursitis considered malignant until proven otherwise

Benign lesion with self-limited growth

Malignant transformation: 1-2% of solitary lesions

Malignant transformation of MHE: 3-5%

Differential Diagnoses

Parosteal Osteosarcoma

Periosteal Chondroma

Chondrosarcoma

Juxtacortical Myositis Ossificans

Subungual Exostosis

Treatment

Surgical resection of symptomatic lesions

Marginal excision including cartilaginous cap and overlying perichondrium

Cartilaginous cap should not be traumatized during resection

Osseous base has minimal activity and may be removed piecemeal