From MedlinePlus Genetics
Adolescent idiopathic scoliosis is an abnormal curvature of the spine that appears in late childhood or adolescence. Instead of growing straight, the spine develops a side-to-side curvature, usually in an elongated "S" or "C" shape; the bones of the spine are also slightly twisted or rotated.

Adolescent idiopathic scoliosis appears during the adolescent growth spurt, a time when children are growing rapidly. In many cases the abnormal spinal curve is stable, although in some children the curve is progressive (meaning it becomes more severe over time). For unknown reasons, severe and progressive curves occur more frequently in girls than in boys. However, mild spinal curvature is equally common in girls and boys.

Mild scoliosis generally does not cause pain, problems with movement, or difficulty breathing. It may only be diagnosed if it is noticed during a regular physical examination or a scoliosis screening at school. The most common signs of the condition include a tilt or unevenness (asymmetry) in the shoulders, hips, or waist, or having one leg that appears longer than the other. A small percentage of affected children develop more severe, pronounced spinal curvature.

Scoliosis can occur as a feature of other conditions, including a variety of genetic syndromes. However, adolescent idiopathic scoliosis typically occurs by itself, without signs and symptoms affecting other parts of the body.  https://medlineplus.gov/genetics/condition/adolescent-idiopathic-scoliosis