This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Diaphyseal aclasis is ? 
Select and explain. 
A. Multiple exostosis, B. Multiple enchondromatosis, C. Multiple hemagioma, D. Multiple osteoid osteoma
A: Multiple exostosis
Answer: A: Multiple exostosis 
Explanation: Ans. is 'a' i.e., Multiple exostosis Hereditary multiple exostoses The ordinary osteochondroma is single; but in the condition known as Diaphysial aclasis (multiple exostosis) the tumor affect several or many bones. Hereditary multiple exostoses is an autosomal dominant hereditary disorder. The risk of malignant changes to a chondrosarcoma is higher in these multiple lesions than in the solitary lesion. Metaphysis of long bones is affected, however, skull and pelvis may also be affected. Multiple exostoses can lead to shoening and bowing of bones; affected individuals often have a sho stature.