The Habsburg Jaw-re-examined

Area of Science:

• Medical history
• Genetics
• Anthropology

Background:

• The "Habsburg Jaw" is a common term for mandibular prognathism or overgrowth.
• This facial characteristic is famously associated with the Spanish Habsburg dynasty.

Purpose of the Study:

• To investigate the etiological basis of the "Habsburg Jaw" by analyzing portraits of Spanish Habsburgs.
• To differentiate between maxillary deficiency and mandibular prognathism as the primary cause of the characteristic facial phenotype.

Main Methods:

• A panel of four investigators assessed representative portraits of Spanish Habsburg rulers.
• They evaluated 11 features of maxillary deficiency and 7 features of mandibular prognathism using a binary scoring system.
• A semi-quantitative scale determined the likelihood of each diagnosis.

Main Results:

• Six out of seven Habsburg rulers showed features indicative of maxillary deficiency (likely or very likely).
• Mandibular prognathism was assessed as likely in 3/7 rulers and unlikely in 4/7.
• The findings suggest maxillary deficiency is a more consistent feature than mandibular prognathism.

Conclusions:

• The characteristic facial morphology of the "Habsburg Jaw" is primarily due to maxillary deficiency.
• This contrasts with the traditional view that mandibular prognathism is the main etiological factor.
• The study re-evaluates the definition and underlying causes of this well-known facial feature.