45,X/46,XX karyotype mitigates the aberrant craniofacial morphology in Turner syndrome.

The aim of this project was to study the impact on craniofacial morphology from Turner syndrome (TS) karyotype, number of intact X chromosomal p-arms, and age as well as to compare craniofacial morphology in TS with healthy females. Lateral radiographs from 108 females with TS, ranging from 5.4 to 61.6 years, were analysed. The TS females were divided into four karyotype groups: 1. monosomy (45,X), 2. mosaic (45,X/46,XX), 3. isochromosome, and 4. other, as well as according to the number of intact X chromosomal p-arms. The karyotype was found to have an impact on craniofacial growth, where the mosaic group, with presence of 46,XX cell lines, seems to exhibit less mandibular retrognathism as well as fewer statistically significant differences compared to the reference group than the 45,X karyotype. Isochromosomes had more significant differences versus the reference group than 45,X/46,XX but fewer than 45,X. To our knowledge, this is the first time the 45,X/46,XX and isochromosome karyotypes are divided into separate groups studying craniofacial morphology. Impact from p-arm was found on both maxillary and mandibular length. Compared to healthy females, TS expressed a shorter posterior and flattened cranial base, retrognathic, short and posteriorly rotated maxilla and mandible, increased height of ramus, and relatively shorter posterior facial height. The impact of age was found mainly on mandibular morphology since mandibular retrognathism and length were more discrepant in older TS females than younger.