Rett syndrome is a rare genetic neurological disorder that occurs almost exclusively in girls. It is characterized by an initial period of normal development, followed by a slowing of developmental milestones. This condition affects many aspects of a person’s life, including their ability to speak, walk, and use their hands.
Common Facial Characteristics
While Rett syndrome is primarily defined by its neurological symptoms, some individuals may develop subtle and specific facial traits. These characteristics are not universal, and their presence can vary significantly from one person to another. Researchers have noted that the face in Rett syndrome does not typically show features like a wide mouth or spaced teeth that are sometimes seen in other neurodevelopmental conditions. Instead, the features are often more understated.
Among the facial characteristics that may be observed are a broad nasal bridge and widely spaced eyes, a feature known as hypertelorism. Some individuals might also have a smaller or more pointed chin and fuller cheeks. Another described trait is a shorter philtrum, which is the vertical groove located between the base of the nose and the upper lip. These features are generally not prominent enough on their own to lead to a diagnosis.
Not every person with Rett syndrome will display all, or even any, of these facial characteristics, as the syndrome’s physical presentation is diverse. Studies involving anthropometric measurements have found that most facial measurements in individuals with the syndrome fall within the normal range. The subtle nature of these traits means they are secondary to the more defining neurological and developmental symptoms.
Progression of Facial Features with Age
The facial characteristics associated with Rett syndrome are not static and evolve as an individual gets older. In early infancy, during the first 6 to 18 months of life, a baby’s facial features are typically unremarkable and show no clear signs of the condition. It is during this time that development may appear to proceed as expected before developmental slowing begins.
The features often become more noticeable between the ages of one and four. This period coincides with what is known as the rapid progressive stage of the syndrome, a time when a child may lose previously acquired language skills and purposeful hand use. As the developmental regression occurs, the subtle facial traits can become more apparent to caregivers and clinicians.
As an individual with Rett syndrome transitions into adolescence and adulthood, their facial structure may continue to change. The face might appear to lengthen, and the characteristics that developed in early childhood can become more pronounced. Despite these changes, the overall pattern of facial measurements tends to remain constant over time relative to the individual’s growth.
Microcephaly and Head Growth
A significant physical sign associated with Rett syndrome is a change in head growth that leads to microcephaly, or a smaller-than-average head size. This is an acquired, or postnatal, condition not present at birth, as an infant who will later be diagnosed often has a normal head circumference.
The hallmark of microcephaly in Rett syndrome is the deceleration of head growth, which typically begins within the first two years of life. This slowing is an important diagnostic marker for clinicians. The rate of growth for the head slows down compared to the standard growth curves for age and sex.
This deceleration in head growth is connected to the genetic basis of the syndrome, most commonly a mutation in the MECP2 gene. This gene provides instructions for making a protein that is important for the development and function of the brain. The resulting smaller head size can sometimes make other facial features appear more pronounced.