<unk>  is a very rare X-linked malformation syndrome caused by mutations in the ephrin-B1 gene (EFNB1). The EFNB1 gene codes for a membrane-anchored ligand which can bind to an ephrin tyrosine-kinase receptor. This ephrin receptor is, amongst other things, responsible for the regulation of embryonic tissue-border formation, and is important for skeletal and craniofacial development. As the ephrin receptor and its EFNB1 ligand are both bound to the (trans)membrane of the cell its cascade is activated through cell-cell interactions. These cell-cell interactions are disturbed due to the presence of cells with the mutant EFNB1 gene, as a result causing incomplete tissue-border formation. Paradoxical to other X-linked conditions, with<unk>  the females are more severely affected than males. This is due to the process of X-inactivation in females, where at random either the maternal or paternal X-chromosome is inactivated in a cell. Due to this process, the body’s tissues contain either cells with normal EFNB1 or the mutated EFNB1. This is called a mosaic pattern. This mosaic pattern of cells 'interferes' with the functionality of the cell-cell interactions, as a result causing the severe physical malformations in females. As with all X-linked conditions<unk>  has a preset chance of being passed down from parents to their offspring. Females have two X-chromosomes and males have one X-chromosome. When a mother is a carrier of<unk> , there is a 50% chance of her passing down the X-chromosome containing the mutated EFNB1 gene to her offspring, regardless if the child is a boy or girl. If the father is a carrier there is a 100% chance of him passing down his X-chromosome with the EFNB1 mutation to a daughter, and 0% chance of him passing it down to a son.
Craniofrontonasal dysplasia
Frontonasal dysplasia
Oculodentodigital dysplasia
Cleidocranial dysostosis
Cranio-lenticulo-sutural dysplasia
Cleft Lip and Palate Association
Thanatophoric dysplasia
Sponastrime dysplasia