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Osteochondromatosis

Background 1. Definition o Inherited, autosomal dominant (AD) disorder with multiple (MO) seen throughout the skeleton o Typically involve the proximal part of the humerus and the distal and proximal portions of femur, tibia, and fibula 2. Related terms o Hereditary multiple exostosis (HME) o Multiple osteochondromas (MO) o Solitary o Familial osteochondromatosis

Pathophysiology 1. Pathology o HME is poorly understood o Curve limitation or constriction bony growth occurs in a direction away from the joint o Cortical overgrowth adjacent to the growth plate 2. Genetic o Autosomal dominant (AD) with near-complete penetrance o Has been associated with mutations in at least 3 different EXT genes o Changes in EXT1 and EXT2 seem to be the most common in HME, are altered in families and function as tumor suppressor genes . EXT1 is in chromosomal 8q23-q24 . EXT2 is on 11p11-p12 . EXT3 is on chromosomal arm 19p 3. Incidence / prevalence o MC benign o 0.9-2/100,000 o Isolated communities . Chamorros of Guam 100/100,000 population . Ojibwa Indian community of Pauingassi, in Manitoba, Canada 1,310 /100,000 population 4. Risk factors o Not due to injuries o White > other races o M = F o Age 2-10 yo 5. Morbidity/mortality o Related to complications assoc. with osteochondromas . Fractures in post-ops (from orthopedic procedures) have been noted . Nerve compression . Blood vessel occlusion . Suspect malignant transformation in adult with rapid growing lesion in a previously stable lesion

Osteochondromatosis Page 1 of 3 4.21.09 Diagnostics 1. History o Painless bump near joints – knee/ shoulder commonly involved o Pedunculated osteochondroma can break, causing pain and swelling to start immediately o Positive family history 2. Physical findings o Asymmetric growth of multiple lumps of long bone of extremities deformities o Leg-length inequality o 2-100 osteochondromas in HME 3. Diagnostic tests o X-ray most common imaging of choice joint abnormal o Lab . Screen for germ-line mutations in EXT1 or EXT2 4. Other studies o CT scan . Useful to assess osteochondromas in pelvic/shoulder/spine o US . May evaluate cartilaginous cap/ complications o MRI . Cartilage on the bony growth . Evaluate possible malignant transformation in case of complaints or growth of lesion after puberty, with evaluation of size of cartilaginous cap

Differential Diagnosis 1. Dysplasia Epiphysealis Hemimelica (DEH, Trevor's disease, tarso-epiphyseal aclasis) o Occurs in infants or young children o Autosomal dominant boys > girls o Symptoms include; pain swelling, joint deformity mostly unilateral o Commonly affect lower limbs > upper o Multiple bone involvement in one limb in about 70% of cases o Dx with plain xray; ossifying o Severe cases assoc with muscle wasting 2. Metachondromatosis (MC) o Rare disorder o Multiple osteochondromas and (benign cartilage cyst/tumor of long bones) in children o Autosomal dominant inheritance o Common in digits and toes (hands and feet respectively) o There is no limb shortening or bone deformity as in multiple osteochondromas 3. (Ollier dz & ) o Multiple cartilage tumors in the medulla bone . Short tubular bones o Predominantly one sided

Osteochondromatosis Page 2 of 3 4.21.09 Management / Therapy 1. Surgical o Only when causing pain or discomfort o Epiphysiodesis (growth plate arrest) of the longer leg . For leg-length inequalities >2.5 cm o Functional complaints . Nerve or vessels compression may require en bloc resection if too large o Cosmetic reasons 2. Genetic counseling o Autosomal dominant o 50% risk of transmission to offspring

Prognosis 1. Life expectancy not affected 2. 1-5% malignant transformation

References 1. http://www.britannica.com/EBchecked/topic/434274/osteochondromatosis 2. Khan A N. Osteochondroma and Osteochondromatosis. eMedicine. http://www.emedicine.com/radio/topic496.htm 3. Bovee J. Multiple osteochondromas. Orphanet Journal of Rare Diseases. 2008:3,3-9. (http://www.ojrd.com/content/3/1/3) 4. http://www.medscape.com/medline/abstract/154465 5. http://www.nwoa.com/patient_education/data/fact/thr_report6cc2.html?Thread_I D=474&;topcategory=General+Information 6. Canale & Beaty: Campbell's Operative Orthopaedics, 11th ed. (http://www.mdconsult.com/das/book/body/102850194- 3/738974787/1584/139.html#4-u1.0-B978-0-323-03329-9..50023-4--cesec6_994) 7. http://ghr.nlm.nih.gov/condition=hereditarymultipleexostoses 8. http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&;part=ext 9. http://ghr.nlm.nih.gov/Resources/patients

Author: John Adiet, MD, Mercy Health System FMRP, WI

Editor: Edward Jackson, MD, Michigan State University-Sparrow Hospital FPRP

Osteochondromatosis Page 3 of 3 4.21.09