Kyphosis is an exaggeration of the normal curve of the thoracic spine. While the spine has a natural S-shaped curve, it can bend in any direction as a result of spinal disorders. Kyphosis causes the appearance of a hump or hunched back and severe pressure in the lungs and abdomen. This disorder is most often caused by osteoporosis but may also be the result of a birth defect or injury. Kyphosis can be treated with medication, support braces or surgery.