exostosis

A cartilage-capped bony projection arising from any bone that develops from cartilage. SEE ALSO: osteochondroma. SYN: hyperostosis (2), poroma (2). [exo- + G. osteon, bone, + -osis, condition]

- e. bursata an e. arising from the joint surface of a bone and covered with cartilage and a synovial sac.

- e. cartilaginea an ossified chondroma arising from the epiphysis or joint surface of a bone.

- hereditary multiple exostoses [MIM*133700] a disturbance of enchondral bone growth in which multiple, generally benign osteochondromas of long bones appear during childhood, commonly with shortening of the radius and fibula; the skull is not involved; the ill effects are usually mechanical but malignant change is rare; autosomal dominant inheritance with genetic heterogeneity of which some cases are due to mutation in the e.-1 gene (EXT1) on 8q. SYN: hereditary deforming chondrodystrophy (1), multiple e., osteochondromatosis.

- ivory e. a small, rounded, eburnated tumor arising from a bone, usually one of the cranial bones.

- multiple e. SYN: hereditary multiple exostoses.

- solitary osteocartilaginous e. SYN: osteochondroma.

- subungual e. painful osseous outgrowths that elevate the nail of the great toe or fingers in young people.

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ex·os·to·sis .ek-(.)säs-'tō-səs n, pl -to·ses -.sēz a spur or bony outgrowth from a bone or the root of a tooth

ex·os·tot·ic -'tät-ik adj

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n.

a benign outgrowth of bone with a cap of cartilage, arising from the surface of a bone. See osteoma.

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ex·os·to·sis (ek″sos-toґsis) [ex- + ostosis] 1. a benign bony growth projecting outward from the surface of a bone. 2. osteochondroma.

Exostosis at the metatarsocuneiform joint.