Apert syndrome is a complex condition caused by premature fusion, or early closure, of one or more of the sutures (specialised joints between skull bones that expand during normal brain growth) that separate the bony plates of the skull.
Apert syndrome (AS) is a frequent form of acrocephalosyndactyly*, which is a group of rare genetic syndromes. It is characterised by craniosynostosis, midface hypoplasia, and finger and toe anomalies and/or syndactyly. Orphanet
Apert syndrome is a condition that affects the craniofacial structures and the limbs.
A syndrome is a disease or disorder that has more than one identifying feature or symptom.
Children with Apert syndrome have bicoronal synostosis, midface hypoplasia and complex syndactyly of the hands and feet.
- Bicoronal synostosis means that both of the coronal sutures of the skull have fused together, causing an abnormal head shape and potentially increased pressure on the growing brain.
- Midface hypoplasia means that the upper two-thirds of the face do not grow normally, causing an abnormal appearance, dental problems (an abnormal bite) and maybe other problems such as sleep apnea.
- Complex syndactyly is a condition in which the fingers and toes are joined together, or webbed, because the bones in the tips of the digits are fused.
- Most children with Apert syndrome have delayed developmental milestones, though this varies from child to child.
- Apert syndrome requires highly specialized treatment by a team of craniofacial medical and surgical subspecialists.
How rare is Apert syndrome?
The estimated incidence of Apert syndrome is reported to be 1/100,000 to 1/160,000 live births. This means it is very rare.
Children generally have extensive structural and functional impairments/disabilities as a result of the malformations of the head and limbs.
Craniosynostosis can lead to acrobrachycephaly or turribrachycephaly with large, late-closing fontanels with a possible impact on brain growth and neurological development. Macrocephaly (increased head circumference) is also found.
Limb involvement in Apert syndrome
Limb malformations mainly consist of soft tissue and bony syndactyly of fingers and toes (involving variable number of digits). The anomalies in the hands are mirror images of each other and are characterized by the following 4 common features:
- Radial deviation of a short thumb as a result of an abnormally shaped proximal phalanx (ie, delta phalanx);
- Complex syndactyly of the index, long, and ring fingers;
- Symbrachyphalangism of the central segments of the index, long, ring, and small fingers; and
- Simple syndactyly of the web space between the ring and small fingers.
Read more about syndactyly in Apert syndrome here.
Other common features of Apert syndrome
Facial findings include midface hypoplasia (where the centre of the face develops more slowly than the eyes, forehead, and lower jaw). In Apert syndrome, the hypoplasia is generally moderate to severe with hypoplasia of the maxilla, shallow orbits, strabismus, hypertelorism, down-slanting palpebral fissures, proptosis, as well as depressed nasal bridge and deviated nasal septum.
Dental findings include delayed appearance of the teeth which may also be impacted and crowded in the mouth with thick, swollen gums. Unilateral and bilateral posterior crossbites are frequent. A posterior crossbite occurs when the top back teeth bite inside the bottom back teeth
Common associated complications include chronic otitis media (ear infections), hearing loss, and increased ocular (eye) pressure that can cause blindness.
Moderate to severe intellectual disability and variable developmental delay are also common in AS (more than 50% of cases). Some patients are also reported to have agenesis of the corpus callosum (see this term), ventriculomegaly, hydrocephalus, fused cervical vertebrae (usually C5-C6), and occasionally cardiac and gastrointestinal defects, radiohumeral synostosis, or ceft velum (see this term).