Published March 18, 2016

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Often, patients inquire about the genetics behind scoliosis. My answer to them is: "It's complicated." It may sound cliché, but it's true. In 2003, the Human Genome Project was completed and promised the possibility for identifying genes associated with each individual person and his or her phenotypes. The project, however, is ongoing, since the sequencing of the genome is one thing, and identifying individual genes responsible for a disease state is another. This is partially due to the genetic concepts of penetrance and expressivity. Penetrance is defined as the degree to which a specific gene or set of genes are manifested in the phenotype (what we see physically), while expressivity is the degree to which a set of genes are expressed.

For example, someone can have a gene for Alzheimer's – however, unless the penetrance for the gene is 100 percent, not everyone with the gene will end up with the disease. An example for expressivity is the gene for spots on a dog. The dog can have large, medium or small spots depending on the expressivity of the gene for spots. With this in mind, you can imagine the difficulty of having definitive diagnostic data based on genetics when there can be variable degrees of penetrance and expressivity. Again, cliché, but "what you see is not always what you get."

Such is the issue with genetic studies that have been done on scoliosis. Familial studies on scoliosis have associated the X chromosome – as well as regions on chromosomes 6, 9, 16 and 17 – with a strong linkage to scoliosis. In addition, familial studies on relatives have also identified a higher incidence of scoliosis in first-degree relatives compared to second- and third-degree relatives. These relationships confirm the genetic etiology of scoliosis. However, genetics alone is not the only culprit. It is likely that scoliosis is a result of a combination of genetics and neurological, environmental and behavioral factors. Studies of identical twins have not always demonstrated both twins having scoliosis despite their identical genetic makeup. In addition, animal studies have demonstrated the ability to induce scoliosis in otherwise straight spines by tethering one side during the growth of the spine.

I can say from my experience that deformities I see abroad have distinct morphologic features compared to those I see in the U.S. Is this a result of genetics or environmental factors? It's difficult to parse out. An additional level of complexity comes about via research associating scoliosis with different white and gray matter characteristics in the brain responsible for processing position sense (proprioception) and genetics research demonstrating mutations in genes associated with somatosensory feedback to the central nervous system.

Regardless of the specific etiology of scoliosis, if you have it, or suspect you have it, my recommendation would be to see a spine surgeon who specializes in scoliosis as soon as possible in order to get "plugged in." During my volunteer work in Africa, I too often saw the consequences of scoliosis cases that have progressed without being adequately monitored, leaving individuals with life-threatening spinal deformities and making corrective surgeries for them unnecessarily complex and risky. Fortunately, in the U.S., adequate follow-up and relatively easy access to health care allows scoliosis to be monitored, ensuring it doesn't progress to such severe states. The majority of scoliosis cases will never need surgery; a small percentage may need to be braced if found in growing children, and an even smaller percentage will need eventual surgical intervention.

How do you know if you have scoliosis? Well, in order to diagnose it, you need an X-ray. However, there are simple and quick methods you can do at home to see if you may have scoliosis. This test is called the forward bending test, and it's performed by bending forward through your hips with your legs straight – as if you're bowing – and allowing your spine to hunch forward. If you don't have scoliosis, both left and right sides of your back will be even.

Since scoliosis is a three-dimensional deformation of the spine, you'll most likely develop a rib hump – or "rib prominence" – if you have scoliosis, making either the left or right side of your back appear higher than the other during this forward bending test. While all asymmetric rib humps don't necessarily equate to scoliosis, it can signal that you may have scoliosis, and an X-ray evaluation and consultation with a specialist may be worthwhile.


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