A scoliosis curve can be C- or S-shaped. In severe cases, the spine will rotate and twist, causing the ribs to stick out more on one side. Most cases of scoliosis are mild and cause no health problems. In severe cases, the twisting of the spine and ribs reduces space within the chest cavity. This can interfere with breathing and put strain on the heart. Untreated scoliosis can also compress and damage the spinal nerves, leading to paralysis.