Clinics and Departments

Laboratory Services

Lab Dept:

Anatomic Pathology

Test Name:


General Information

Lab Order Codes:



Exostoses 1 and 2; Hereditary multiple osteochondromata; Multiple cartilaginous exostoses; Diaphyseal aclasis; HME

CPT Codes:

81479 – Molecular Pathology Unlisted procedure
88271 x10 – Molecular cytogenetics, DNA probe, each

Test Includes:

Using genomic DNA obtained from the submitted specimen, bi-directional sequence of all 11 coding exons of the EXT1 gene is obtained and analyzed. Concurrently, targeted array CGH analysis with exon-level resolution (ExonArrayDx) is performed to evaluate for a deletion or duplication of one or more exons in both the EXT1 and EXT2 genes. Mutations found in the first person of a family to be tested are confirmed by repeat analysis using sequencing, restriction fragment analysis, or other appropriate method.


Test Indications:

Individuals with HME often develop benign cartilage-capped tumors (exostoses) at the ends of the long bones or the surface of flat bones. Exostoses develop prior to skeletal maturity only. Bony deformity, bowing of the long bones, limited range of motion, and premature osteoarthrosis may be associated with hereditary multiple exostoses (HME). Exostoses also may cause complications by putting pressure on nearby tissues, nerves or blood vessels. A rare but severe risk in patients with mutiples exostoses is the development of malignant chondrosarcoma, which in 1-5% of patients.
Mutation in the EXT1 gene seems to be associated with a more severe disease and higher risk of developing chondrosarcoma than EXT2 mutations.

Reasons for referral:
1. Confirmation of a clinical diagnosis
2. Genetic counseling

Lab Testing Sections:

Anatomic Pathology - Sendouts

Referred to:

GeneDx, Inc. (GDX#: 1813)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours (Preferred draws are Sunday - Thursday as specimens can only be received at the reference lab Monday - Friday. Specimens collected Friday or Saturday will be held for shipment on Monday.)

Turnaround Time:

6 weeks for new patients

Special Instructions:

A GeneDx signed request form must be sent with any patient or specimen to the laboratory.


Specimen Type:

Whole blood


Lavender top (EDTA) tube

Draw Volume:

1 - 5 mL blood

Processed Volume:

Same as Draw Volume


Routine venipuncture for blood specimens, invert gently to mix

Special Processing:

Lab Staff: Send whole blood in original collection container labeled with patient name, date of birth and medical record number, including signed consent form and requisition, with a cool pack, via overnight or second-day courier so that the sample will arrive at GeneDx, Inc. on a weekday (Monday through Friday). Samples drawn on Friday or Saturday should be held at refrigerated temperatures for shipment on Sunday. Cool packs should be used in warm weather. Do not freeze.
Specimens may be stored at refrigerated temperature for up to 7 days prior to shipping.

Patient Preparation:


Sample Rejection:

Unrefrigerated specimens older than 48 hours; clotted or hemolyzed for blood; frozen specimens; mislabeled or unlabeled specimens


Reference Range:

No mutations detected

Critical Values:



Buccal brushes cannot be accepted for this testing.


Bi-directional sequence analysis


GeneDx, Inc. February 2012


2/6/13: CPT update

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