Angelman syndrome is a genetic disorder that affects the nervous system and causes intellectual and physical disabilities. It develops in infants right after conception, due to defects in the UBE3A gene.
Affected children can show symptoms of Angelman syndrome as young as 6 to 12 months, but most patients are diagnosed between the ages of 9 months and 6 years. Early on, symptoms are sometimes confused with autism or cerebral palsy, which are more common than Angelman syndrome.
Distinctive physical features
The physical features vary among patients, and different patients have unique combinations of physical indicators.
The most common physical indicator of Angelman syndrome, seen in about 80% of patients, is a smaller-than-normal head circumference, known as microcephaly. Usually, microcephaly is not present at birth, but develops within the first three years of life.
Some children also develop a flat occiput, which is the bone that makes up the back of the skull, as their skull ossifies (hardens) in early life.
Patients may have a wide smile with gaps between their teeth, coarse facial features, and a pale complexion with light-colored hair, known as hypopigmentation. Scoliosis, or curvature of the spine, also is common in Angelman syndrome.
Patients and especially children with Angelman syndrome are easily excitable and frequently laugh, smile, and gesture with animated hand flapping movements for no apparent reason, and more often than typically-developing children. This animated behavior often is accompanied by the tongue sticking slightly out of the mouth.
Children with Angelman syndrome often have abnormal sleep cycles or a lessened need for sleep, which manifests as frequent waking in the night or early in the morning. Hyperactivity and a short attention span also are common.
Less-common symptoms include crossed eyes, involuntary eye movements known as nystagmus, sensitivity to heat, and an unusual fascination with water.
Movement, coordination issues
More than 95% of Angelman syndrome patients develop movement and balance disorders, specifically ataxia (impaired balance or coordination) and unsteady and jerky movement of limbs.
The development of motor skills in children is significantly delayed. Most children with Angelman syndrome do not walk until they are 3 or 4 years old, and they often have a distinctive gait characterized by jerky, marionette-like movements. In certain advanced cases, patients may not learn to walk until later in life; as many as one in 10 patients may be unable to walk.
Seizures occur in more than 80% of patients, and typically manifest before age 3.
Feeding problems during infancy may develop due to sucking and swallowing issues and to atypical tongue movements, which are characteristic of Angelman syndrome. Uncontrolled drooling is common.
Issues with communication may become apparent as early as 6-months-old. The majority of affected babies do not start to babble until after their first birthday.
Receptive communication aptitudes are typically higher than verbal skills. In other words, children with Angelman syndrome often are able to understand language spoken to them to a greater extent than they are themselves able to speak.
Most patients continue to have limited speech or no speech capabilities throughout their lives; however, most are able to communicate nonverbally. Adults with Angelman syndrome usually can communicate through gesturing or with the use of communication boards.
Symptoms over time
Although the majority of symptoms associated with Angelman syndrome typically remain for the entirety of a patient’s life, a few symptoms have been documented as improving as patients age. These include:
- the tendency to need less sleep than other children or have issues falling and staying asleep;
- seizures, which usually do not disappear, but become less frequent and severe;
- excitability, hyperactivity, and short attention span.
Puberty occurs normally in people with Angelman syndrome. The condition does not affect fertility.
Adults with Angelman syndrome usually arevnot able to live independently, but most are able to live at home or in home-like placements.
People with Angelman syndrome have a roughly normal life expectancy, with some patients living into their 60s or 70s.
Last Updated: April 30, 2021
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