|Year : 2017 | Volume
| Issue : 6 | Page : 594-595
Hereditary multiple exostoses
Hasan Ekim1, Meral Ekim2
1 Department of Cardiovascular Surgery, Bozok University School of Medicine, Yozgat, Turkey
2 Department of Nutrition and Dietetics, Bozok University School of Health, Yozgat, Turkey
|Date of Submission||14-Mar-2017|
|Date of Acceptance||15-May-2017|
|Date of Web Publication||17-Jan-2018|
Dr. Hasan Ekim
Bozok University, School of Medicine, Department of Cardiovascular Surgerys Yozgat
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Ekim H, Ekim M. Hereditary multiple exostoses. Med J DY Patil Univ 2017;10:594-5
Hereditary multiple exostoses (HME) are a heterogenous skeletal disorder involving the growth plates of many skeletal elements. It is characterized by the presence of two or more cartilage-capped bony tumors and also known as multiple osteochondromas. Most of them had a positive family history. The number and size of exostoses increase during childhood till closure of the epiphysis or metaphysis. Although the true prevalence of HME is not exactly known, it is estimated at one of every 50 000 births.
HME may be found not only in human but also found in some animals such as horse, cat, cattle, and dog. Even a dinosaur fossil with a large tumor on the scapula was found.
Although the HME may be originated from anywhere in skeletal system, this disorder most commonly affects joints of the extremities. Osteochondromas are localized in up to 80% of patients in the distal forearm. They are localized less frequently in the proximal forearm. In lower limbs, they may involve any bone but most frequently occur in the lower metaphysis of the femur. Lower limbs may be malformed due to exostoses as reported in an article (Congenital multiple congenital exotosis with congenital heart disease) published in this issue of the journal. Osteochondromas develop by intramembranous ossification. Therefore, they are rarely located in tarsal and carpal bones, and never seen in the facial bones.
Most HME cases are mainly caused by heterozygous loss of function mutations into two genes (EXT1 or EXT2) that encode glycosyltransferases responsible for heparan sulfate synthesis leading to heparan sulfate deficiency. These mutations have been found in 40%–94% of patients. EXT1 and EXT2 were identified on chromosome 8 (locus 8q24.1) and chromosome 11 (locus 11p11–13), respectively.
The mature osteochondromas may lead to impingement of surrounding tissues and neurovascular structures. Many patients suffer from pain. Although pain may be linked with compression of neurovascular structures, tendons, and muscles; in some patients, there is no clear relation between pain and HME. The deformities resulting from the forearm and wrist osteochondromas often cause impaired function. Bone deformities and short stature are considered important cosmetic problems.
The HME can be diagnosed by plain X-ray when at least two osteochondromas are present at the juxtaepiphyseal region of long bones. MRI displays the relationship of the disease to important neurovascular structures and joints.
The most severe complication of HME is malignant transformation (chondrosarcomas or osteosarcomas). According to recent series, its incidence ranges from 0.6% to 2.8%. Malignant transformation can be life-threatening because of their typical resistance to chemotherapy and radiotherapy. Malignant transformation should be suspected if the cartilaginous cap exceeds 2 cm in thickness. The whole body MRI can be used to rule out or detect malignant transformation of HME into chondrosarcoma.
The irregular sharp spikes of HME can be the potential cause for peripheral arterial injuries and associated pseudoaneurysm formation. Compression of the vascular structures due to a growing osteochondroma may lead to pseudoaneurysm formation, thrombosis, claudication, and ischemia. The development of pseudoaneurysm is the most common vascular complication (56%). Other important vascular complications are vascular compression (16%) and arterial thrombosis (14%).
Compression of peripheral nerves may cause paresthesia and pain. Vertebral exostoses may cause medullary compression.
Although costal exostoses are mostly asymptomatic, they can rarely cause cardiothoracic complications, such as hemithorax, pneumothorax, and even acute coronary syndrome.
Spontaneous regression of the HME has been reported in single cases. Surgical intervention should be performed in symptomatic patients. Many patients with HME can be operated on successfully with radical surgical excision. However, the resection of the tumors in the pelvis may be difficult or even impossible due to involvement of neurovascular structures by very large chondrosarcomas. Following surgical excision, local recurrences may develop due to incomplete surgical resection or the development of a new osteochondromas. In addition, there is a significant risk for the development of broad scar formation after surgery. Therefore, detailed informed consent indicating possible keloid formation risk should be obtained preoperatively in all patients or their relatives.
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