Patient's question:
I am a patient with multiple osteochondromas. I also deeply understand the psychological impact this disease can have on people. As someone who has gone through it, I don't want my daughter to suffer from this pain. How can this disease be prevented?Doctor's answer:
Multiple hereditary osteochondromas have three characteristics: ① they are hereditary ② bone shortening or deformity ③ a high incidence of malignant transformation into peripheral chondrosarcoma. The ratio compared to solitary osteochondromas is 1:10. Due to the hereditary feature, the onset of symptoms is earlier than in solitary osteochondromas, generally occurring before the age of 10. Mild cases (especially in females) can remain latent throughout life. It is more common in males, with a male-to-female ratio of 2:1.Approximately 2/3 of cases show a hereditary pattern. If one parent has multiple hereditary osteochondromas, about half of their offspring will inherit the condition, with it being more common in male offspring. In families with this condition, if a male member is normal, he will not pass it on to his descendants; conversely, in the same family, even normal females can pass on the disease. In other words, in males, both the disease and the ability to inherit it are expressed simultaneously; in females, the disease can be latent or mild but can still be passed on to offspring.
It is generally diffuse and symmetrical, and all bones undergoing endochondral ossification can be sites for osteochondromas. The metaphyseal ends of growing bones are most commonly affected, with multiple and larger osteochondromas, particularly near the knees, shoulders, hips, wrists, and ankles, but they are rare and mild when occurring in the elbows. Multiple hereditary osteochondromas are also common in the axial skeleton, occurring near the ossification centers of the second or epiphyseal bones. In the scapula, they primarily occur along the vertebral margin, the inferior angle, the acromion, the glenoid, and the coracoid. In the pelvis, they primarily occur along the iliac crest. In the spine, they are mainly located on the spinous and transverse processes. In the ribs, they are more common at the costochondral junctions or posterior ends. Except for the calcaneus, which has a secondary ossification center, multiple hereditary osteochondromas do not occur in the carpal or tarsal bones, as their development is similar to that of the epiphyses.
Multiple, relatively symmetrical exostoses can be seen and felt. In more severe cases, their appearance is characteristic, and diagnosis can be made based on physical examination alone. In more severe cases, limb shortening may occur, sometimes very significant and diffuse, resembling achondroplasia. However, multiple hereditary osteochondromas do not have the features of achondroplasia, and cartilage growth function is normal. In fact, limb shortening is not due to abnormal cartilage growth but rather to the consumption of cartilage proliferative potential by extramedullary exostoses (osteochondromas), which prevents it from being used for bone elongation. Due to this uneven distribution of circumference and composition along the diaphysis and the two bones of the upper and lower limbs, limb shortening is often accompanied by deformities, such as varus or valgus deformities of the knees, ankles, elbows, and wrists. The most typical deformities occur in the forearm and chest. Because osteochondromas are more common in the wrists than in the elbows, and because 3/4 of bone elongation occurs at the distal end of the humerus and 4/5 at the proximal end of the radius, the ulna is always shorter than the radius, resulting in a deformity where the radius protrudes laterally and posteriorly, leading to ulnar deviation, and occasionally radial head dislocation.
Prognosis
Like solitary osteochondromas, multiple hereditary osteochondromas stop growing when growth in the body ceases. If an osteochondroma grows significantly in adulthood in an individual case, it is usually a sign of sarcomatous transformation, with an incidence of about 25%. Multiple hereditary osteochondromas typically transform into sarcomas after the age of 15.