The Habsburg Jaw-re-examined.

"Habsburg Jaw" is a frequently used eponymous designation for patients with mandibular prognathism, hyperplasia, or overgrowth. The purpose of this study was to evaluate portraits of the Spanish Habsburgs to determine the relative contributions of maxillary deficiency and mandibular prognathism to overall facial appearance. Representative portraits of the Spanish Habsburgs were assessed by 4 investigators for the presence of 11 anatomic features of maxillary deficiency and 7 of mandibular prognathism. Each characteristic was given a binary score of 1 if present and 0 if absent. Thus, the maximum score would be 11 for maxillary deficiency and 7 for mandibular prognathism. A semi-quantitative scale was established to determine the likelihood of each diagnosis: Maxillary deficiency: 0-4.99 (unlikely), 5-7.99 (likely), 8-11 (very likely); mandibular prognathism: 0-2.99 (unlikely), 3-5.99 (likely), 6-7 (very likely). Six of 7 Habsburg rulers were considered either likely or very likely to have maxillary deficiency, whereas 3/7 were assessed as likely and 4 unlikely to have mandibular prognathism. The results of this study suggest that the primary deformity of the "Habsburg Jaw" is maxillary deficiency rather than absolute mandibular prognathism.