PATTERN OF MALFORMATIONS IN THE AXIAL SKELETON IN HUMAN TRIPLOID FETUSES

We examined the axial skeleton in 15 human triploid fetuses (10 with X XX and 5 with XXY sex chromosomes). All fetuses 14-29 weeks of gestati onal age (GA), underwent whole-body radiography, permitting analysis o f the nasal bone and the spine. From 9 of these, detailed radiographs were taken of midsagittal blocks of the cranial base and the spine, pe rmitting detailed analysis of the cranial base. Nasal bone: Of 14 fetu ses, where the nasal bone was seen on lateral projection, it appeared short in 10 cases. Spine: The spine was normal in 7 of 15 fetuses; mal formations occurred in 8. These were osseous fusions between 2 or more vertebral bodies, most frequently in the cervical and thoracic region s, and disproportions in the sizes of the cervical bodies. Fusions occ urred in 5 cases alone, and in one case in combination with disproport ions of vertebral size. Disproportions alone occurred in 2 cases. Cran ial base: Malformation of the basilar part of the occipital bone was f ound in 5 of the 9 fetuses investigated. Of 9 fetuses, bilateral ossif ication centers of the postsphenoid bone occurred in 7, and shell-like ossification centers in 2. There was no difference in the type of mal formations in the different axial fields related to genotype (XXX and XXY). Conclusion: The most remarkable findings in the axial skeleton o f triploid fetuses are vertebral fusions in 6 of 15 cases; clefts of v ertebral bodies, previously reported as common findings in trisomy fet uses, are not demonstrated. (C) 1997 Wiley-Liss, Inc.