Apert syndrome is a rare genetic condition identified at birth, characterized by distinct physical manifestations affecting the skull, face, and limbs. This condition arises from specific genetic changes that influence how bones develop, leading to premature fusion of certain bones. Understanding the characteristics of Apert syndrome, its occurrence rates, and its genetic underpinnings can provide clarity on this complex disorder.
Understanding Apert Syndrome
Individuals with Apert syndrome exhibit a combination of physical characteristics, stemming primarily from the premature fusion of skull bones, a condition known as craniosynostosis. This early fusion prevents the skull from growing normally, leading to an affected head shape, often appearing tall or pointed with a high forehead. The unusual skull development also influences facial features, resulting in a sunken appearance in the middle of the face, a beaked nose, and widely spaced, sometimes bulging, eyes.
Another feature is syndactyly, which involves the fusion of fingers and toes. This fusion can range in severity from webbed skin to the complete joining of bones, often affecting multiple digits on both hands and feet. For instance, the middle three fingers are commonly fused, and in some cases, all fingers may be conjoined, creating a “mitten” or “rosebud” hand appearance. Beyond these primary skeletal effects, individuals with Apert syndrome may experience other related concerns, including dental problems, hearing loss, and breathing difficulties due to structural anomalies in the face and airways.
Prevalence and Occurrence
Apert syndrome affects approximately 1 in 65,000 to 88,000 live births globally. This condition affects male and female infants in roughly equal proportions. The incidence can increase with advanced paternal age, suggesting a link between the father’s age and new genetic mutations. The birth prevalence is consistently low across different populations, estimated at around 15.5 per 1,000,000 births.
Genetic Basis
Apert syndrome is caused by mutations in the fibroblast growth factor receptor 2 (FGFR2) gene. This gene provides instructions for creating a protein called FGFR2, which plays a significant role in the development of bones by signaling immature cells to become bone cells. In Apert syndrome, mutations within the FGFR2 gene lead to an altered protein that signals too actively, promoting the premature fusion of bones in the skull, hands, and feet.
The condition follows an autosomal dominant inheritance pattern. However, nearly all cases of Apert syndrome result from new, spontaneous mutations that occur during the formation of reproductive cells in a parent or in early embryonic development, rather than being inherited from an affected parent. More than 98% of cases are linked to two specific mutations in the FGFR2 gene.
Diagnosis and Early Recognition
Apert syndrome is diagnosed at birth based on the presence of its characteristic physical features. The combination of an unusually shaped skull and fused fingers and toes provides the initial indication. The distinct fusion patterns of the fingers and toes help differentiate Apert syndrome from other conditions that might also involve premature skull bone closure.
In some instances, the condition may be suspected before birth through prenatal diagnostic methods. Ultrasound examinations can reveal signs such as an abnormally shaped skull, a prominent forehead, or fused digits. Magnetic resonance imaging (MRI) can also assess fetal skeletal development. A definitive diagnosis is confirmed through genetic testing, which involves analyzing DNA for the specific FGFR2 gene mutations associated with Apert syndrome.