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Year |
2001 |
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Question Number |
256 |
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Category |
Select |
Question
Which of the following conditions is considered a common clinical manifestation of multiple hereditary exostoses?
1- Radial bowing
2- Scoliosis
3- Acetabular dysplasia
4- Genu varum
5- Dwarfism
Figures
Answer (click for answer)
Preferred response: 1
Exostoses, or osteochondromas, are osteocartilagenous projections from bone resulting from dysplastic growth at the peripheral growth plate. They are the most common benign bone tumor and are often asymptomatic. The heredity predisposition to these tumors is called Multiple Heredity Exostoses and has a prevalence of one in 50, 000 in the study sited. It is inherited in an autosomal dominant fashion and may be more severely expressed in males. There is a small risk of malignant transformation of these lesions into chondrosarcomas (1-2%). However, the multiplicity of the lesions in these patients means they have 1000-2500 times the risk of chondrosarcoma when compared to an individual without the disease. The most common exostoses that transform are those involving the pelvis or shoulder girdle.
The hallmark of this condition is reduction of osseous growth and bony deformity. 75% of affected individuals have an osseous deformity, the most common of which involves the forearm (50% in one study, 30-60% in another), followed by the ankle (45%), and knee (20%). The characteristic forearm deformity is that of severe ulnar shortening with angular deformity of the distal aspect of the radius and bowing of the radial shaft. This is associated with ulnar deviation of the wrist and often subluxation or dislocation of the radial head. These deformities can appear quite severe cosmetically but are surprisingly well tolerated in terms of forearm function. Most studies, including two cited here, have not shown significant improvement in functional scores after surgical correction of deformity in this condition. Therefore, surgery (usually consisting of an ulnar lengthening procedure and/or stapling of the radial physis) is only recommended for cosmetic reasons currently.
In regard to the question, radial bowing is the most common manifestation listed. Deformities about the knee are also quite frequently encountered (i.e.; genu varum), however 20% I guess is not common enough to be correct (and forearm deformity is the hallmark of the disease which is definitely what they were looking for). Short stature is present is 40% of affected individuals, but the condition is not associated with true dwarfism. Acetabular dysplasia and scoliosis are not commonly associated with multiple hereditary exostoses.
Reference: Stanton RP, Hansen MO: Function of the upper extremities in hereditary multiple exostoses. J Bone Joint Surg Am 1996;78:568-573.
Arms DM, Stecker WB, Manske PR, Schoenecker PL: Management of forearm deformity in multiple hereditary osteochondromatosis. J Pediatr Orthop 1997;17:450-454.
Schmale GA, Conrad EU III, Raskind WH: The natural history of hereditary multiple exostoses. J Bone Joint Surg Am 1994;76:986-992.