Smith-Magenis Syndrome

What is Smith-Magenis syndrome?

Smith-Magenis syndrome is a developmental condition that affects several parts of your child’s body. Some of the main symptoms include abnormal cognitive development (intellectual disability), unique facial features, behavioral concerns and difficulty sleeping. Smith-Magenis syndrome occurs because a small piece of a chromosome, carrying an important gene, is deleted from your child’s DNA during embryonic development.

Who does Smith-Magenis syndrome affect?

Smith-Magenis syndrome can affect anyone, as the genetic change occurs at the time of conception when the egg and sperm meet. There’s usually no history of the condition in your biological family line. This is known as a spontaneous or “de novo” mutation.

In rare cases, your child may inherit the condition from a biological parent who doesn’t have symptoms of the condition but has a genetic change in some of their sex cells but not all of their cells. This type of inheritance is called germline mosaicism.

How common is Smith-Magenis syndrome?

Smith-Magenis syndrome affects 1 out of every 15,000 to 25,000 people worldwide.

What are the symptoms of Smith-Magenis syndrome?

Symptoms of Smith-Magenis syndrome affect multiple organ systems in your child’s body. They range in severity from mild to severe. Common symptoms include:

• Abnormal cognitive development (intellectual disability).
• Short stature.
• Scoliosis.
• Limited sensation of pain or temperature.
• Raspy or hoarse voice.
• Hearing and/or vision problems.
• Excessive weight gain.

Symptoms that affect infants include:

• Weight gain during adolescence.
• Weak muscle tone.
• Developmental delay.
• Poor reflexes.
• Feeding challenges.
• Frequent crying.
• Long naps and daytime drowsiness.

Although rare, severe cases of Smith-Magenis syndrome can affect the function of your child’s heart and kidneys. It can also cause seizures.

Facial features

People born with Smith-Magenis syndrome have characteristic facial features that become more apparent during middle childhood. These features include:

• A square-shaped face.
• Full cheeks.
• Sunken eyes.
• Downward slanting mouth (frown).
• A flat nasal bridge.
• Protruding of the lower jaw.

Some children and adults diagnosed with Smith-Magenis syndrome have dental abnormalities due to their facial structure.

Sleep disturbances

Smith-Magenis syndrome can make sleeping difficult for infants, children and adults diagnosed with the condition. Sleep disturbances include:

• Difficulty falling asleep and staying asleep.
• Excessive daytime sleepiness.
• Frequent nighttime awakenings.

The change in sleep patterns relates to melatonin secretion in individuals with Smith-Magenis syndrome.

Emotional or behavioral symptoms

Children diagnosed with Smith-Magenis syndrome can display certain emotional or behavioral symptoms, including:

• Affectionate personality.
• Self-hugging.
• Frequent tantrums or outbursts.
• Aggression (hand/wrist biting, head banging, hitting).

They may also have conditions that affect their behavior like ADHD or autism spectrum disorder.

What causes Smith-Magenis syndrome?

Changes to the retinoic acid-induced 1 gene (RAI1) cause Smith-Magenis syndrome. The RAI1 gene is responsible for producing proteins that give your cells instructions to do their job throughout your body. This gene isn’t completely understood, but studies suggest that this gene creates proteins for several parts of your child’s body, which is why symptoms of Smith-Magenis syndrome are so broad.

A chromosome deletion (a portion containing the RAI1 gene) or a mutation of the RAI1 gene itself causes Smith-Magenis syndrome. Nearly 90% of children diagnosed with the condition are missing the RAI1 gene, which is part of the short arm (p) of chromosome 17 (17q11.2).

The chromosome deletion is spontaneous (de novo) and happens randomly when the egg and sperm meet at conception. In very rare cases, chromosomes from the egg and sperm break apart and trade places with each other (translocation). These rare cases happen very early during the development of an embryo. The remaining 10% of those diagnosed have a genetic mutation of the RAI1 gene, which causes a change in the structure of the child’s DNA at that specific gene location.

How is Smith-Magenis syndrome diagnosed?

A diagnosis of Smith-Magenis syndrome usually occurs during childhood when symptoms become more apparent. Your child’s provider will ask questions to learn more about their symptoms, take a complete medical history and examine your child. A genetic blood test is necessary to confirm a diagnosis and rule out similar conditions.

How is Smith-Magenis syndrome treated?

Treatment for Smith-Magenis syndrome focuses on relieving symptoms of the condition, which could include:

• Enrolling your child in early intervention (before age 3) and educational programs (after age 3) to help your child meet developmental and academic milestones.
• Encouraging your child’s active participation both at home and in the community.
• Participating in outpatient therapies such as speech-language therapy, behavioral therapy, physical therapy and/or occupational therapy.
• Taking medications to treat specific symptoms of co-existing conditions such as ADHD or disordered sleep.
• Wearing glasses to correct vision problems.
• Getting tubes surgically placed in your child’s ears to prevent infections and monitor for hearing loss.
• Eating a healthy, well-balanced diet and exercising regularly to manage weight.

Your child’s provider will individualize their treatment to fit your child’s needs to help them thrive.

Who treats Smith-Magenis syndrome?

Your child will likely need a team of medical professionals to treat symptoms of Smith-Magenis syndrome that affect different parts of their body. Their care team could consist of:

• Pediatrician and pediatric specialists.
• Surgeon.
• Ophthalmologist.
• Audiologist.
• Psychologist.
• Nutritionist.
• Speech pathologist.
• Occupational therapist and physical therapist.

Does melatonin treat Smith-Magenis syndrome sleep disturbances?

Melatonin is a hormone within your body that helps you go to sleep. Melatonin supplements can help your child fall asleep and regulate their sleep-wake cycle. If your child has trouble sleeping because of Smith-Magenis syndrome, melatonin supplements can help them get a better night’s sleep if they take the supplement before bed. If your child has trouble sleeping, talk to their provider to make sure melatonin supplements are right for them.

How can I prevent Smith-Magenis syndrome?

You can’t prevent Smith-Magenis syndrome because the condition is genetic. Changes to your child’s DNA happen randomly and unpredictably. Medical, physical and behavioral interventions are available to help your child manage their symptoms and live a full life.

What can I expect if my child has Smith-Magenis syndrome?

The prognosis for Smith-Magenis syndrome is dependent on the severity of your child’s symptoms. Some people diagnosed with the condition have a normal life span and can live semi-independently with limited support from their family, friends and caregivers. Others might need more support throughout their entire life and benefit from living in a group setting or a residential care community. Symptom management and preventative care is lifelong to help your child live a healthy and full life.

Is there a cure for Smith-Magenis syndrome?

No, there isn’t a cure for Smith-Magenis syndrome. The condition occurs randomly due to changes to your child’s DNA. Your child’s provider will offer individualized treatment options to help with symptom management throughout your child’s life span.

When should I see my child’s healthcare provider?

Visit your child’s healthcare provider if your child:

• Is self-injuring or overly aggressive.
• Misses developmental milestones for their age.
• Is experiencing increased distress or impairment at home and/or school.
• Isn’t able to sleep at night or has trouble staying awake during the daytime.

When should I go to the ER?

Visit the emergency room if your child:

• Has a seizure.
• Has an irregular heartbeat.
• Isn’t able to eat or stay hydrated.

What questions should I ask my doctor?

• How can I support my child?
• What should I do if my child misses developmental milestones?
• Are there symptoms I should look out for?
• How do I keep my child safe if they throw a tantrum?
• Are there side effects to the recommended treatment options?

A note from Cleveland Clinic

It can be difficult to learn that your child has a developmental condition that affects several parts of their growing body. Many parents and caregivers find comfort in participating in support groups for Smith-Magenis syndrome. Your child’s provider will offer management options for their symptoms to help your child reach their fullest potential. While there isn’t a cure for Smith-Magenis syndrome, lifelong support is available through your child’s care team.