The protruding jawbone may be caused by several reasons: First, it may be due to genetic factors. Some patients have a longer and wider jaw bone than normal due to genetic factors. However, this condition is a physiological state and not a disease. Second, this condition may be caused by an old injury to the jawbone. For example, the patient has suffered a violent blow to the face that produced a fracture of the mandible. During the recovery process, the bony deformity of the jaw may be produced, resulting in a more prominent jaw bone. Third, it may be caused by an occupying lesion. For example, the presence of a bone tumor may cause a bony protrusion here. Fourth, this condition may also be caused by acromegaly. This condition is often seen in patients who have reached adulthood and still have a high level of growth hormone production. This can lead to continued growth of short bones within the body. In the face, the short bones like the maxilla and mandible continue to grow and become more prominent.