Craniofrontonasal dysplasia (craniofrontonasal syndrome, craniofrontonasal dysostosis, CFND) is a very rare X-linked malformation syndrome caused by mutations in the ephrin-B1 gene (EFNB1). Phenotypic expression varies greatly amongst affected individuals, where females are more commonly and generally more severely affected than males. Common physical malformations are: craniosynostosis of the coronal suture(s), orbital hypertelorism, bifid nasal tip, dry frizzy curled hair, longitudinal ridging and/or splitting of the nails, and facial asymmetry.The diagnosis CFND is determined by the presence of a mutation in the EFNB1 gene. Physical characteristics may play a supportive role in establishing the diagnosis. The treatment is always surgical and is based on each patients specific phenotypic presentation. Presentation
Phenotypic expression varies greatly between individuals with CFND. Some of the more prominent characteristics are:
Craniosynostosis of the coronal suture(s) (fusion of the coronal sutures),
Orbital hypertelorism (increased interocular distance),
Bifid nasal tip,
Dry frizzy curled hair,
Longitudinal ridging and / or splitting of the nails,
Facial Asymmetry.Other characteristics that are less frequently seen are: broad nasal base, low anterior hair line, low set ears, crowding of the teeth, maxillary hypoplasia, rounded and sloping shoulders, pectus excavatum, scoliosis, high arched palate, orbital dystopia, low implant of the breasts with asymmetric nipples and volume, webbed neck, hand or foot abnormalities such as clinodactyly (most common is a curved 5th finger) and cutaneous syndactyly (webbed fingers / toes).Females are more commonly and usually more severely affected than males. Males can however have (some of) the same symptoms as females, but this is not frequently seen.
Most males have mild symptoms such as hypertelorism and a broad nasal base with bifid nose, but can also be a carrier of the mutation yet stay clinically unaffected. Genetics
CFND 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 CFND 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 CFND has a preset chance of being passed down from parents to their offspring. Females have two X-chromosomes and males have one X-chromosome.