|
Year |
2001 |
|---|---|
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Question Number |
178. |
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Category |
Select |
Question
Which of the following systemic conditions is associated with a genetic defect in skeletal formation that does not involve abnormal collagen?
1- Osteogenesis imperfecta
2- Spondyloepiphyseal dysplasia congenita
3- Achondroplasia
4- Multiple epiphyseal dysplasia
5- Kneist dysplasia
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Answer (click for answer)
Answer – 3
Achondroplasia is an autosomal dominant defect involving the FGF receptor 3 gene and is manifested as a quantitative cartilage defect in the proliferative zone of the physis. The collagen produced is normal.
Osteogenesis imperfecta is caused by a defect in type I collagen. The collagen is cross-linked abnormally and the genes involved are COL 1A1 and COL 1A2.
Spondyloepiphyseal dysplasia and multiple epiphyseal dysplasia both involve qualitative collagen defects, the latter involving a cartilage oligomeric matrix protein and the former being linked to a COL 2A1 defect. Kneist dysplasia is an autosomal dominant defect of the COL 2A1 gene.
Reference: Miller, Review of Orthopaedics. 3rd edition 2000.