Adolescent idiopathic scoliosis (AIS) is an abnormal curvature of the spine that affects 2 to 4 percent of young people aged 10 to 18. It is most often asymptomatic, though some patients with severe deformity may notice that a change in alignment affects the fit of their clothes or the look of their silhouettes.
The type of curvature varies by patient. Some find that the torso develops a lateral lean, which causes the patient to have difficulty standing straight. Others notice an asymmetry in the height of the shoulders or hips. Perhaps most noticeable and characteristic of scoliosis, however, is the development of a rib hump or elevated shoulder blade in the back of the body.
As the term idiopathic indicates, medical science has not yet identified the causal process in AIS. However, because 30 percent of patients have a family history of the condition, a genetic predisposition is highly likely. Researchers are currently investigating potential causal processes, including hormonal and muscle imbalances as well as asymmetric growth patterns, and are working toward identifying the genes that contribute to the condition.