Hereditary multiple Osteochondromas is a rare disorder that affects bone growth. Bony tumors (exostoses or osteochondromas), covered with cartilage, typically appear in the growth zones (metaphyses) of the long bones adjacent to the areas where tendon and muscles attach to the bone. These growths vary in size and number among affected individuals, even within the same family. Some individuals will present with a few large “lumps” while others will show several small growths. The median age of diagnosis is three years and almost all affected individuals are diagnosed by 12 years of age.
In many cases, no treatment is required. If the exostoses are small, they may have little or no effect on the patient. However, in more severe cases, the growths may cause deformities of the forearm, knees, ankles, spine and/or pelvis. They may impose upon nerves, tendons and/or blood vessels, and interfere with movement or circulation, causing substantial Pain as a result of pinched nerves or compressed tendons.
Bones that develop exostoses most often are the upper arm (humerus), forearm, knee and shoulder blades (scapulae). Bowing of the forearm and ankle are the problems that most often require surgical correction.
Approximately 40 percent of affected individuals have Mild Short stature as a result of shortened and/or bowed legs. If the vertebrae are affected, spinal cord compression may result, causing Numbness and/ or paralysis. Urinary obstruction has been observed due to exostoses of the pelvic area.
The bony growths that characterize this disorder continue to grow until shortly after puberty at which time normally new growth no longer develops. The risk for development of malignant (cancerous) tumors, mostly chondrosarcomas, is approximately 1 to 5%.