Prognathism is a positional relationship of the mandible or maxilla to the skeletal base where either of the jaws protrudes beyond a predetermined imaginary line in the coronal plane of the skull.

[citation needed] In humans, non-pathological maxillary and alveolar prognathism can occur due to normal variation among phenotypes.

[citation needed] Maxillary prognathism affects the middle third of the face, causing the maxilla to jut out, thereby increasing the facial area.

Prognathism can also be used to describe ways that the maxillary and mandibular dental arches relate to one another, including malocclusion (where the upper and lower teeth do not align).

[5] Harmful habits such as thumb sucking or tongue thrusting can result in or exaggerate an alveolar prognathism, causing teeth to misalign.

[citation needed] Prognathism, if not extremely severe, can be treated in growing patients with orthodontic functional or orthopaedic appliances.

Mandibular prognathism is a potentially disfiguring genetic disorder where the lower jaw outgrows the upper, resulting in an extended chin and a crossbite.

[15] The process of portrait-mapping has provided tools for geneticists and pedigree analysis; most instances are considered polygenic,[16] but a number of researchers believe that this trait is transmitted through an autosomal recessive type of inheritance.

Charles II of Spain, who lived 1661 to 1700, is said to have had the most pronounced case of the Habsburg jaw on record,[18] due to the high number of consanguineous marriages in the dynasty preceding his birth.