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Hereditary Osteochondroma


Hereditary multiple osteochondromas (HMO), also known as hereditary multiple exostoses (HME) are benign cartilage-capped bone tumors that grow outward from the metaphyses of long bones. HMO can lead to the shortening and bowing of bones; affected individuals often have a short stature. Depending on their location the exostoses can cause the following problems: pain or numbness from nerve compression, vascular compromise, inequality of limb length, irritation of tendon and muscle, as well as a limited range of motion at the joints upon which they encroach, and premature osteoarthrosis. The lifetime risk for malignant osteochondrosarcoma is low (1-5%), but the risk increases with age.

HMO is an autosomal dominant hereditary disorder; meaning a patient with HMO has a 50% chance of transmitting this disorder to his or her children. Most individuals with HMO have a parent who also has the condition, however, approximately 10% -20% of individuals with HMO have the condition as a result of a spontaneous mutation and are thus the first person in their family to be affected.

We provide testing for Multiple Exostoses Type 1 and Type 2.

Type OMIM Gene/Protein Description

Exostoses, multiple, type 1

133700 EXT1/Exostosin-1

Mutations of EXT1 are the most common cause of HMO. About 200 mutations in the EXT1 gene have been identified in people with hereditary multiple exostoses type 1. These mutations prevent any functional exostosin-1 protein from being made. The loss of exostosin-1 protein function prevents it from forming a complex with the exostosin-2 protein and adding heparan sulfate to proteins.

Exostoses, multiple, type 2



Exostosis-2 binds to Exostosis-1 to form a complex that modifies a protein called heparan sulfate so it can be used in the body. Heparan sulfate is involved in regulating a variety of body processes including the formation of blood vessels and blood clotting. It also has a role in the spreading of cancer cells. More than 90 mutations in the EXT2 gene have been identified in people with hereditary multiple exostoses type 2.  Most of these mutations prevent any functional exostosin-2 protein from being made.

Methodology: Sequencing of entire coding region

Purpose: Confirmation of Clinical Diagnosis

ICD-10 Code Q99.9

Test Requisition: Sequencing Requisition

EXT1 CPT Code: 81479 Cost: $836.00

EXT2 CPT Code: 81479 Cost: $836.00

Panel CPT Codes: 81479x2 Cost: $1672.00

Turn-around-time: 4-5 weeks

Specimen Requirements

Shipping Information


1. Schmale GA, Conrad EU, Raskind WH (July 1994). "The natural history of hereditary multiple exostoses". J Bone Joint Surg Am 76 (7): 986–92.

2. CANNON JF (1954). "Hereditary multiple exostoses". American Journal of Human Genetics 6 (4): 419–25. PMC 1716573.

3. Cook A, Raskind W, Blanton SH, Pauli RM, Gregg RG, Francomano CA, Puffenberger E, Conrad EU, Schmale G, Schellenberg G (1993). "Genetic heterogeneity in families with hereditary multiple exostoses". American Journal of Medical Genetics 53 (1): 71–9.

4. Wu YQ, Heutink P, de Vries BB, Sandkuijl LA, van den Ouweland AM, Niermeijer MF, Galjaard H, Reyniers E, Willems PJ, Halley DJ (1994). "Assignment of a second locus for multiple exostoses to the pericentromeric region of chromosome 11". Human Molecular Genetics 3 (1): 167–71.

5. Le Merrer M, Legeai-Mallet L, Jeannin PM, Horsthemke B, Schinzel A, Plauchu H, Toutain A, Achard F, Munnich A, Maroteaux P (1994). "A gene for hereditary multiple exostoses maps to chromosome 19p". Human Molecular Genetics 3 (5): 717–22.

6. Wuyts W, Van Hul W (2000). "Molecular basis of multiple exostoses: mutations in the EXT1 and EXT2 genes.". Hum. Mutat. 15 (3): 220–7.

7. Porter DE, Lonie L, Fraser M, Dobson-Stone C, Porter JR, Monaco AP, Simpson AH (2004). “Severity of disease and risk of malignant change in hereditary multiple exostoses. A genotype-phenotype study”. J Bone Joint Surg Br.86(7):1041-6.



Contact Information
Genetics Laboratory
University of Oklahoma Health Sciences Center
1122 NE 13 Street, Suite 1400, Oklahoma City, OK 73104
Phone: (405) 271-3589 |Fax: (405) 271-7117 Email: Dr. Shibo Li

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