Alternative names
Extended chin


Prognathism is a protrusion of the jaw (mandible) due to misalignment of teeth caused by malformations of the shape of the bones of the face.


Prognathism may cause malocclusion (misalignment of the biting surfaces of the upper and lower teeth), giving some people an angry or fighter’s appearance. Prognathism may be a symptom of various syndromes or conditions.

Common Causes
A protruding jaw can be part of the normal facial shape a person is born with. It can also be caused by inherited conditions such as Crouzon syndrome or basal cell nevus syndrome. You can develop it as a child or adult from causes such as gigantism or Acromegaly.

Home Care

It is appropriate to see a dentist or orthodontist to treat abnormal alignment of the jaw and teeth. However, also contact your primary health care provider to rule out medical disorders that can be associated with prognathism.

Call your health care provider if

  • there is difficulty talking, biting, or chewing related to the abnormal jaw alignment.  
  • you have concerns about jaw alignment

What to expect at your health care provider’s office
The medical history will be obtained and a physical examination performed.

Medical history questions documenting prognathism in detail may include:

  • Is there any family history of an unusual jaw shape?  
  • Is there difficulty talking, biting, or chewing?  
  • What other symptoms are also present?

Physical examination will include a detailed examination of the mouth and jaw, and examination for signs of disorders that can be associated with prognathism.

Diagnostic tests may include:

After seeing your health care provider:
You may want to add a diagnosis related to prognathism to your personal medical record.

Johns Hopkins patient information

Last revised: December 6, 2012
by Dave R. Roger, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.