Apert syndrome is a genetic disorder characterized by skeletal abnormalities. A key feature of Apert syndrome is the premature closure of the bones of the skull (craniosynostosis). This early fusion prevents the skull from growing normally and affects the shape of the head and face. In addition, a varied number of fingers and toes are fused together (syndactyly).

Craniosynostosis causes many of the characteristic facial features of Apert syndrome. Premature fusion of the skull bones prevents the head from growing normally, which leads to a sunken appearance in the middle of the face (midface hypoplasia), a beaked nose, a wrinkled forehead, and an opening in the roof of the mouth (a cleft palate). In individuals with Apert syndrome, an underdeveloped upper jaw can lead to dental problems, such as missing teeth, irregular tooth enamel, and crowded teeth.

Many individuals with Apert syndrome have vision problems due to eye abnormalities, which can include bulging eyes (exophthalmos), wide-set eyes (hypertelorism), outside corners of the eyes that point downward (downslanting palpebral fissures), eyes that do not look in the same direction (strabismus), and shallow eye sockets (ocular proptosis). Some people with Apert syndrome have hearing loss or recurrent ear infections due to malformed ear structures.

Abnormal development of structures in the face and head can also cause partial blockage of the airways and lead to breathing difficulties in people with Apert syndrome. Craniosynostosis also affects development of the brain, which can disrupt intellectual development. Cognitive abilities in people with Apert syndrome range from normal to mild or moderate intellectual disability.

Individuals with Apert syndrome have syndactyly of the fingers and toes. The severity of the fusion varies, although the hands tend to be more severely affected than the feet. Most commonly, three digits on each hand and foot are fused together. In the most severe cases, all of the fingers and toes are fused. Rarely, people with Apert syndrome may have extra fingers or toes (polydactyly). Some people with Apert syndrome have abnormalities in the bones of the elbows or shoulders. These bone problems can restrict movement and impede everyday activities. In some people, abnormalities occur in both sides of the body, but in others, only one side is affected.

Additional signs and symptoms of Apert syndrome can include unusually heavy sweating (hyperhidrosis), oily skin with severe acne, or patches of missing hair in the eyebrows.

• Turribrachycephalic skull shape (cone-shaped or towering skull) which is visisbly apparent and can be confirmed by skull radiograph or head CT examination
• Characteristic facial features including moderate-to-severe underdevelopment of the midface, bulging and wide-set eyes, "beaked" nose, underdeveloped jaw and shallow eye sockets
• Variable hand and foot findings such as syndactyly of the fingers and toes and polydactyly

• Craniosynostosis release, also called cranial vault expansion (surgery to treat the fusion of the skull bones too early in development). This is typically done at 6 to 12 months of age if the infant has normal intracranial pressure (pressure inside the skull), or earlier if the pressure is increased. In some cases, the surgeon performs an initial procedure in the first year of life to increase space within the skull before the release, in which case the release may be done after 12 months of age.
• Midface advancement or correction, in those who need additional correction of the skull or face for problems such as a sunken appearance of the face (midface hypoplasia), abnormal shape of the skull, or abnormal positioning of the eyes (orbital dystopia). The timing of surgery for midface advancement may vary depending on each child's situation. For example, it may be recommended before the child enters school (or around 4 to 8 years of age) so as to improve appearance, with the goal of maximizing the psychological well-being of the child. However, having this surgery at this age may result in recurrence, requiring another surgery in late adolescence. Therefore, some surgeons recommend midface advancement several years later, when facial growth is almost complete and the rate of recurrence is lower.
• Hypertelorism correction to lessen the distance between widely-spaced eyes. This may be done by removing part of the bone between the eyes (interorbital bone), and repositioning the eye sockets (orbits) closer together for improved appearance.