Apert Syndrome Health Article

Definition

Premature closure of the skull bones leading to facial distortion with an unusually tall skull and fusion of the fingers and toes, known as syndactyly, are the major features of Apert syndrome (AS). Another name for this disorder is acrocephalysyndactyly.

Description

A French physician E. Apert first reported in 1906 the syndrome that bears his name. He detailed the skull malformation, midface hypoplasia (underdevelopment) and the hand abnormalities. The hand appears mitten-shaped because of the finger fusion. Intelligence varies from normal to severe mental retardation.

Genetic profile

Apert syndrome (AS) is an autosomal dominant disorder, meaning that a person only has to inherit one nonworking copy of the gene to manifest the condition. In most cases, AS is sporadic meaning that the parents are usually unaffected, but a fresh mutation or gene change occurring in the egg or sperm was passed onto the affected child. For these families the chance to have another affected child is very low. An affected parent has a 50% chance of passing on the abnormal gene to their child, who will then also have Apert syndrome.

Two unique mutations in the fibroblast growth factor receptor 2 (FGFR2) gene located on chromosome 10 were discovered in 1995. This gene directs the development of bone formation. When parental studies were performed, genetic researchers determined that the father passed on the gene causing AS and was usually older than 30 years. No explanation has been found for this unusual finding.

After comparing the physical findings with gene mutations causing AS, researchers noted that one mutation resulted in a much more improved facial appearance after corrective surgery. The other mutation produced a more severe form of syndactyly.

Demographics

Apert syndrome has been estimated to occur in one of every 60,000-160,000 births. All races and both sexes are equally affected.

Signs and symptoms

At birth the craniofacial (pertaining to the skull and face) appearance is striking. Early or premature closure of the skull sutures (layer of fibrous tissue connecting the skull bones) makes the skull grow taller than normal with a short distance from the front to the back of the head. Always it is the coronal suture connecting the frontal and parietal bones that fuses early. The buildup of pressure on the brain is minimal because the fontanelles, or soft spots, and midline of the skull remain open. Due to the small space within the eye sockets, the eyeballs bulge outward and to the side. Also, the eyelids have a downward slant and cannot completely close.

From the middle of the eye sockets to the upper jaw, the face is sunken in or concave when viewed from the profile. This midfacial hypoplasia causes the upper jaw to slope backward pushing the lower teeth in front of the back teeth.

The mouth area has a prominent mandible (lower jaw), down-turned corners, high arched palate, cleft palate

(an opening in the roof of the mouth), crowded upper teeth, poor contact between the upper and lower teeth, delayed tooth eruption.

Syndactyly of the fingers and toes involves not only soft tissues but also the bones, nerves, and tendons. Flexing of the fingers and toes after the first digit is not usually possible. The thumb can be unattached or fused to the other fingers. Also, the other fingers may or may not be fused to each other in varying degrees. Fusion of the toes is less worrisome. Correction only becomes necessary when walking is difficult.

Most children with AS are noisy breathers. The nose and airways leading to the lungs are smaller than usual. These narrow passageways probably make breathing more difficult. At night if breathing is more troublesome, sleep apnea can occur. This stoppage of breathing while sleeping deprives the brain and body of oxygen. Mental impairment can occur as a result of oxygen deprivation.

Excessive sweating is often seen. Researchers do not know why the sweat glands are overactive. As the children reach puberty, they develop excessive acne. A skin specialist or dermatologist can help to control it.

The height and weight of children with AS is usually normal. However, their learning ability can be affected. A small number of children with Apert syndrome will have a normal level of intelligence while the majority will have some degree of mental retardation.