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Latest Science Behind Hereditary Bone Condition

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Every now and then, when you rub your hand along a bone, you may feel some odd dents and bumps. That's normal. But some people have many bony bumps or protuberances called exostoses or osteochondromas. This could be part of an inherited condition called multiple hereditary exostoses.

In this article, orthopedic surgeon Kevin B. Jones from Primary Children's Medical Center at the University of Utah brings us up-to-date on the science of multiple hereditary exostoses. Using colorful diagrams, X-rays, and photographs, we get a clear idea of the type of problems multiple hereditary exostoses can cause.

When something goes wrong in the gene that controls bone growth, the cells don't line up in well-ordered stacks like they are supposed to. Instead, they form uneven, irregular outgrowths of bone. These bony outgrowths are usually covered with a cap made of cartilage.

Most of what we know about the biochemistry, cellular biology, and molecular biology of this condition comes from studies of fruit flies, zebrafish, and mice. Don't laugh! The genetic structure and miscoding of the involved cells are remarkably similar

The result of the altered bone growth can be one bone growing longer than another or deformity as one bone curves too much. Some children have growth disturbances that give them an odd appearance (e.g., arms or legs too short compared with the spine). In rare cases, the osteochondromas become malignant. The cancerous bone is slow growing and can be removed so it's not usually life-threatening.

How is this condition treated? Sometimes no treatment is required. The bony outgrowths aren't painful and don't cause any problems. In some cases, the bone growths are removed.

The major area of concern is the deformities -- not just because they can limit function, but also because of the cosmetic effect on children. Surgery is often needed to correct bone alignment, put a dislocated joint back in place, and manage differences in leg- or arm-length.

It may be possible to prevent some dislocations by surgically cutting a ligament before the uneven pull has a chance to have its full effect. Exostoses of the spine can put pressure on the spinal cord or spinal nerve roots causing neurologic problems. Once again, by removing these bony overgrowths, the problem is prevented.

In the future, it may be possible to design medications that could interrupt the extra bone growth. A better understanding of the hereditary links and cellular biology is required before pharmacologic prevention can be developed. Why some bones are affected more often than others is another mystery that needs to be solved in order to prevent deformities and dislocations.

Reference: Kevin B. Jones, MD. Glycobiology and the Growth Plate: Current Concepts in Multiple Hereditary Exostoses. In Journal of Pediatric Orthopaedics. July/August 2011. Vol. 31. No. 5. Pp. 577-586.

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