Question: What is (are) Hereditary multiple osteochondromas ?
Answer: Hereditary multiple osteochondromas (HMO) (formerly called hereditary multiple exostoses) is a genetic condition in which people develop multiple benign (noncancerous) bone tumors that are covered by cartilage (called osteochondromas). The number and location of osteochondromas varies greatly among affected individuals. These tumors are not present at birth, but almost all affected people develop multiple osteochondromas by the time they are 12 years old. Once the bones stop growing, the development of new osteochondromas also usually stops. Osteochondromas can cause abnormal growth of the arms, hands, and legs, which can lead to uneven limb lengths (limb length discrepancy) and short stature. These tumors may cause pain, limit joint movement, and exert pressure on nerves, blood vessels, and surrounding tissues. Osteochondromas are typically benign; however, researchers estimate that people with HMO have about a 1% lifetime risk of these tumors becoming a cancerous osteochondrosarcoma. HMO is caused by mutations in the EXT1 and EXT2 genes and is inherited in an autosomal dominant pattern.
Source: GARD

Question: Is Hereditary multiple osteochondromas inherited ?
Answer: How is hereditary multiple osteochondromas inherited? HMO is caused by mutations in the EXT1 and EXT2 genes. It is inherited in an autosomal dominant pattern, which means that one copy of the altered gene in each cell is sufficient to cause this condition. In most cases, an affected individual inherits the mutation from one affected parent. Other cases result from new mutations in the gene and occur in people with no history of the condition in their family. Most affected individuals (96%) that have inherited a gene mutation from their parent show signs and symptoms of this condition. However, the family history may appear negative because of the failure to recognize the disorder in family members and/or reduced penetrance. Reports have suggested that some females may not show clinical features of HMO but still have the gene mutation that causes this condition.
Source: GARD

Question: How to diagnose Hereditary multiple osteochondromas ?
Answer: Is genetic testing available for hereditary multiple osteochondromas? GeneTests lists the names of laboratories that are performing genetic testing for hereditary multiple osteochondromas. To view the contact information for the clinical laboratories conducting testing for the EXT1 gene, click here. To view the contact information for the clinical laboratories conducting testing for the EXT2 gene, click here. Please note: Most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional. Below, we provide a list of online resources that can assist you in locating a genetics professional near you. How might malignant transformation in hereditary multiple exostoses (HME) be diagnosed? Surface irregularities and unorganized chalk deposits with light areas in the middle of the tumor and cartilage cap may be seen on a bone scan, ultrasound or preferably an MRI. However the diagnosis of chondrosarcoma can only be confirmed by a bone biopsy. What are the signs and symptoms of malignant transformation in hereditary multiple exostoses (HME)? A doctor may become suspicious of a malignant transformation if there is an increase in the size of the tumor in adults when bone growth is already complete. In addition, cancer should be suspected if the thickness of the cartilaginous cap of the osteochondroma is over 1-2 centimeters (normally, after bone growth is complete, the cap is only a few millimeters thick). Other signs of a malignant transformation may include bone pain, temporary loss of sensory or motor function due to compression of a nerve (neurapraxia) or pressure related symptoms in nearby organs. Is screening recommended for malignant transformation in hereditary multiple exostoses (HME)? At present, medical researchers agree that more studies need to be performed to determine the best screening protocols for those with HME, including the study of benefit/cost/risk. However a compelling study was published in 2014 by Czajka and DiCaprio which compares the screening of malignant transformation in people with HME to the screening of breast and cervical cancer in women. The authors conclude that screening should be offered to individuals with HME over the age of 16 (or when bone growth has been completed). They propose screening should include a thorough clinical examination and a full body MRI every two years. If an MRI is not possible than a bone scan be performed, followed by an ultrasound of the cartilage cap of any suspicious findings. The Czajka and DiCaprio further recommend that individuals with HME should be made aware of warning signs of malignant transformation and taught self examination techniques.
Source: GARD