Twins' Curved Backs Suggest a Genetic Role in Scheuermann's Disease
Many people are aware of scoliosis, a sideways curvature of the spine. But there is another kind of curvature called kyphosis. Kyphosis is a "C-shaped" curve as seen from the right side of the spine. The person can even look "stooped over." This is a condition called hyperkyphosis.

The most common cause of hyperkyphosis in the upper spine is Scheuermann's disease. This condition occurs when the front part of three or more vertebrae in a row become wedge-shaped. Doctors don't know what causes Scheuermann's, but the two most likely theories are genetic and mechanical factors.

A genetic or inherited cause hasn't been proved yet. Scientists haven't been able to find the exact gene that carries this trait. A report of identical twins with Scheuermann's supports the idea of genetic cause. Two 14-year-old brothers who are identical twins both have all the signs of Scheuermann's disease.

In this condition, the curve is greater than 45 degrees, with at least one vertebra wedged 5 degrees or more. One twin has a 48-degree curve. The other has a much larger curve (74 degrees). Each boy has three vertebrae in a row that are wedged. There have been no strains or mechanical loads on the spine in either boy. It's most likely that these brothers inherited this condition.

Researchers aren't sure why these two brothers have such different curves. It's possible that the boy with the larger curve has a mutated or damaged Scheuermann's gene. If scientists can find the exact gene that causes this deformity, treatment could begin earlier in life. Early treatment could help avoid the possibility of disability later in life.
References
Ham C. A. Graat, MSc, et al. Classical Scheuermann Disease in Male Monozygotic Twins. In Spine. November 15, 2002. Vol. 27. No. 22. Pp. E485-E487.