Angelman syndrome is a rare genetic disorder that impacts the nervous system. It is caused by a problem with the UBE3A gene on chromosome 15, which in most cases occurs by chance around the time of conception. This condition results in a range of developmental and physical symptoms. The signs are not apparent at birth but begin to emerge within the first year of life.
Key Developmental and Intellectual Characteristics
Developmental delays are the first indication, becoming noticeable between six and twelve months of age. During this period, parents might observe that their child is not reaching common milestones such as sitting without support or making babbling sounds. These early delays are a precursor to what will become a more significant intellectual disability.
The developmental trajectory for children with Angelman syndrome involves severe learning difficulties. As they grow, the gap between their development and that of their peers widens. The intellectual disability associated with the condition is profound, and individuals require lifelong care and support.
While intellectual disabilities are a consistent feature, the specific presentation can vary among individuals. Low muscle tone, or hypotonia, is another common early symptom that contributes to developmental delays. Feeding difficulties in infancy, such as problems with sucking and swallowing, can also be present, sometimes making it hard for the child to gain weight.
Distinctive Physical and Movement Symptoms
One of the most defining characteristics of Angelman syndrome is a disorder of movement and balance known as ataxia. This results in a walking pattern, or gait, that is often stiff and jerky. Children may walk with their arms held up in the air, and their movements can appear uncoordinated. Tremulous motions of the limbs are common.
Many individuals with Angelman syndrome have distinct facial features. A small head size, or microcephaly, is a common characteristic, with head growth often slowing down and plateauing around two years of age. Other features can include a wide mouth with widely spaced teeth and a prominent chin. Some individuals may also have a tendency to stick their tongue out.
Beyond facial features and gait, other physical signs may be present. Paler skin, hair, and eye color compared to other family members can occur, which is associated with the loss of a specific gene called OCA2 on the same chromosome affected in the syndrome.
Unique Behavioral and Communication Traits
Individuals with Angelman syndrome often exhibit a unique behavioral profile characterized by a happy and excitable demeanor. This includes frequent smiling and laughter, which can occur with little or no stimulus. This excitability is often accompanied by hand-flapping movements, especially when they are happy or agitated.
A short attention span and hyperactivity are also common behavioral traits. Children may appear restless and have a fascination with certain things, such as water. As individuals age, the excitability may lessen, but the core behavioral traits often remain.
Communication is severely affected in Angelman syndrome. Most individuals develop very limited or no verbal speech. While their ability to speak is impaired, their receptive language skills, which is the ability to understand what is being said, are generally stronger. They often learn to communicate effectively through nonverbal methods such as gestures, signs, or other augmentative communication systems.
Associated Medical Conditions
A high percentage of individuals with Angelman syndrome experience seizures. These seizures, also known as epilepsy, typically begin before the age of three. The management of seizures is a primary focus of medical care and can sometimes require lifelong treatment.
Sleep disturbances are another common issue. Individuals with the condition often have a decreased need for sleep and may experience abnormal sleep-wake cycles. This can be challenging for caregivers, though sleep problems may improve as the individual gets older.
Other medical conditions can also be present. Strabismus, or crossed eyes, is a frequent finding. Scoliosis, which is a side-to-side curvature of the spine, can develop and may worsen over time, potentially impacting mobility. Gastrointestinal issues, such as constipation and reflux, are also commonly reported among individuals with Angelman syndrome.