EOS can be caused by neuromuscular conditions, birth defects of the spine, underlying syndromes, and in some cases, the cause is unknown. Most patients face a high risk of spinal deformity progression due to the early onset of their condition when skeletal growth is remaining. When the spinal deformity crowds the space within the chest cavity, or when the chest cavity is malformed, lung growth can be impaired during a critical time of development.

Extremely progressive EOS can result in heart problems, and a life-threatening pulmonary condition known as thoracic insufficiency syndrome (TIS). It is important to treat EOS particularly when patients are diagnosed with, or at risk of, TIS to help resolve the potential for lifelong health complications.