Eugene Apert is credited with first describing the clinical triad of craniosynostosis, midface hypoplasia, and symmetric syndactyly of the hands and feet. Apert's syndrome has been observed in white, black, and Asian populations, and more than 500 cases have been recorded to date.

The prevalence of Apert's syndrome is approximately 15.5 in 1 million births. Apert's syndrome accounts for 4.5% of all cases of craniosynostosis. Inheritance is autosomal dominant with an equal male-to-female gender ratio. Most cases represent new mutations. The rarity of familial instances can be explained by the reduced genetic fitness of the affected individual. New mutations are thought to be exclusively of paternal origin.

The craniofacial dysmorphism in affected individuals is extensive with macrocrania universally seen. The head is deformed with a broad, high forehead and brachycephaly present while premature closure of the sutures (coronals most frequently) is seen with radiographic examination. The midface hypoplasia results in hypotelorism as well as a depressed nasal bridge and downsloping palpebral fissures. Ocular manifestations secondary to decreased orbital size include proptosis, amblyopia, strabismus, papilledema, and optic atrophy. The incidence of hypoplasia of the corpus callosum, agenesis of the septum pellucidum, and cavum septum pellucidum is significant and developmental delays are common.

In addition to craniosynostosis and midface hypoplasia, symmetric syndactyly is required to establish an accurate diagnosis of Apert's syndrome. The most common type of syndactyly found in Apert's syndrome is fusion of digits 2, 3, and 4, with digits 1 and 5 being free. The second most common type is fusion of digits 2, 3, 4, and 5, with digit 1 being free. The fused digits usually have a single common nail. The syndactyly of the feet is analogous to that observed in the hands and is remarkably symmetric. Other skeletal abnormalities are common and include partial/complete duplication of the first metatarsals, multiple epiphyseal dysplasia, various shoulder and elbow deformities, a short and broad femoral neck, single/multiple vertebral fusions, and ankylosis of the major joints.

Concurrent visceral abnormalities are not uncommon and include cardiovascular anomalies (10%), genitourinary anomalies (10%), and abnormalities of the respiratory and alimentary tract.