Craniofacial patterning in Klinefelter (47 XXY) adults.

Radiographic cephalometry incorporating a pattern profile analysis was used to compare 26 adult Klinefelter males from Finland with first degree adult relatives, 15 males and 14 females. Compared with female relatives, the 47 XXY males were larger in almost all craniofacial linear dimensions, but were similar in facial shape apart from greater mandibular prognathism. Mandibular dimensions in particular differed between the Klinefelter and unaffected males, the corpus length being larger, the ramus shorter and the gonial angle more obtuse in the 47 XXY group. The prominent facial profile, most marked in the mandible, was a dominant feature of the Klinefelter subjects who also displayed a more acute median cranial base angle than each control group. Generally, Klinefelter morphology was marked by greater variability or patterning of the craniofacial structures compared with relatives, possibly due to decreased developmental canalization. It is proposed that the 47 XXY complex may affect endochondral growth in the cranial base, as well as having a direct influence on jaw growth.