Apert syndrome

Apert Syndrome, virtually synonymous with Acrocephalosyndactyly, is a branchial arch syndrome, resulting from a developmental anomaly. Specifically, this syndrome affects the first branchial (or pharyngeal) arch, which is the precursor of the maxilla and mandible. Since the branchial arches are important developmental features in a growing embryo, disturbances in its development create lasting and widespread effects.

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Overview

In 1906, Eugène Apert, a French physician, first described nine people with a similar disorder. Since he was the first to do so, his name is associated with the syndrome.^[1]

Breaking down the name of this disorder, “acro” means “peak” in Greek and refers to the “peaked” heads of some people with this syndrome. Syndactyly refers to the webbing of fingers and toes.

What occurs in embryology is that hands and feet are supposed to have some selective cells die (known as selective cell death or apoptosis to separate the fingers and toes. In the case of acrocephalosyndactyly, selective cell death does not occur, and fusion of skin, and sometimes bone, between the fingers and toes occur.

As in Crouzon syndrome and Pfeiffer syndrome, the bones of the skull are affected as well. Craniosynostosis results from the infant’s skull and facial bones fusing early while in development, disrupting normal bone growth. Fusion of different sutures lead to different patterns of growth of the skull. Examples include: trigonocephaly (fusion of the metopic suture), brachycephaly (fusion of the coronal suture), dolichocephaly (fusion of the sagittal suture), plagiocephaly (fusion of coronal and lambdoidal sutures unilaterally), oxycephaly (or turricephaly- fusion of coronal and lambdoid sutures).

Causes

There is some support that acrocephalosyndactyly occurs in an autosomal dominant mode, but the basic defect is still unknown. Evidence for this is that males and females are affected equally.

Nonetheless, almost all cases are sporadic, signifying that most are attributable to fresh mutations or an environmental insult to the genetic code. Offspring of a parent with Apert syndrome stand a 50% chance of inheriting the condition.

In 1995, A.O.M Wilkie, along with other researchers, published a paper showing evidence of a relationship between acrocephalosyndactyly and a gene, called Fibroblast growth factor receptor 2, on chromosome 10.

There is also some evidence that the age of the father is related to this syndrome. This stands in stark contrast to Down Syndrome, where the age of the mother is positively correlated with the risk of having a child with the syndrome. It is speculated that older fathers are more likely to have mutations in the chromosomes of their sperm, but a correlation to this disorder has not been established through scientific research.

Symptoms

The cranial malformations are the most apparent effects of acrocephalosyndactyly. Cranial synostosis occurs, as explained above, with Brachiocephaly being the common pattern of growth. Additionally, a common characteristic is a high, prominent forehead and a flat posterior skull. Due to the premature closing of sutures of the skull, increased cranial pressure develops which sometimes leads to mental deficiency. Nonetheless, this is not always the case since some of these people possess normal intelligence. Furthermore, a flat or concave face may develop because of a deficient growth in the mid-facial bones, leading to a conditir prognathism. Other features of acrocephalosyndactyly may be shallow bony orbits and broadly spaced eyes.

Low-set ears is also a typical characteristic, as is with all of these disorders that are called branchial arch syndromes. The reason for this is that in fetal life all ears are much lower than what we are accustomed to seeing. During normal development, the ears "travel" upward on the head but, in these cases, the ears do not follow this normal pattern of development since these syndromes have the greatest effects on the head.

The major attribute of this syndrome is syndactyly of the hands and feet. Commonly there is fusion of fingers or toes with usually an equal amount on both sides. It is usual for the middle 3 fingers to be fused together. This appearance is the characteristic for which acrocephalosyndactyly is named. The thumb and big toe may be broad and malformed. This disorder is progressive with age as the joints continue to appear present but are immovable.

Treatments

Surgery is needed to prevent the closing of sutures in the skull from damaging brain development. Combined orthodontic and orthognathic surgery can help to relieve some of the facial deformities, such as the flat or concave face. In particular, the LeFort III, a surgical procedure, can be used to detach the midface from the rest of the skull to reposition it appropriately. Additionally, aggressive surgery is needed to separate as many fingers and toes as possible in life.

Dental significance

For dentists, this disorder is very important to understand since most of the physical abnormalities are presented in the head, and particularly the oral cavity. Common relevant features of acrocephalosyndactyly are a high-arched palate, pseudomandibular prognathism (appearing as mandibular prognathism), a short width of the palate, and crowding of the teeth.

See also

• Crouzon syndrome
• Pfeiffer syndrome
• Hearing loss with craniofacial syndromes
• Saethre-Chotzen syndrome

References

1. ^ synd/194 at Who Named It