Protruding lower jaw, considered a disorder only if it affects chewing, speech, or social function.Encyclopedia Entry for Prognathism :Prognathism. Prognathism may cause malocclusion (misalignment of the biting surfaces of the upper and lower teeth). It can give a person an angry, or fighter's appearance. Prognathism may be a symptom of other syndromes or conditions.An extended (protruding) jaw can be part of a person's normal face shape that is present at birth. It can also be caused by inherited conditions, such as Crouzon syndrome or basal cell nevus syndrome. It may develop over time in children or adults as the result of conditions such as gigantism or acromegaly.A dentist or orthodontist may be able to treat abnormal alignment of the jaw and teeth. Your primary health care provider should also be involved to check for underlying medical disorders that can be associated with prognathism. Call a provider if: You or your child have difficulty talking, biting, or chewing related to the abnormal jaw alignment. You have concerns about jaw alignment.The provider will perform a physical exam and ask questions regarding your medical history. Questions may include: Is there any family history of an unusual jaw shape? Is there difficulty talking, biting, or chewing? What other symptoms do you have? Diagnostic tests may include: Skull x-ray (panoramic and cephalometric) Dental x-rays Imprints of the bite (a plaster mold is made of the teeth) This condition may be treated with surgery. An oral surgeon, plastic facial surgeon, or ENT specialist may perform this surgery.Extended chin.Prognathism Prognathism Malocclusion of teeth Malocclusion of teeth.Goldstein JA, Baker SB. Cleft and craniofacial orthognathic surgery.