The vertebral column derives from somites, transient paired segments of mesoderm that surround the neural tube in the early embryo. The formation of the vertebrar involves many processes including resegmentation of the rostral and caudal regions of adjacent somites that then fuse to form vertebral elements. Disruption of these processes can a cause of severe segmentation defects of the vetebrae. The frequency of segmentation defects of the vetebra has been estimated at 0.5 of 1000 births. The range of segmentation defects includes left-right uneven formation of somites that results in hemivertebrae or wedge vertebrae. Incomplete segmentation can result in fused segments such as block vertebrae. A failure of the process of resegmentation and migration of the sclerotomal compartment can result in a failure of midline fusion, such as butterlfy vertebrae.

HP:0005705

human_phenotype

HP:0003422