smith-magenis syndrome


Smith-Magenis Syndrome (SMS) is a rare developmental disorder that affects many parts of the body. It is estimated to occur in between 1 out of every 15,000 to 25,000 births. SMS is caused by an alteration to, or loss of, some genes on chromosome 17.

People with SMS have characteristic developmental, behavioural and physical features. Some of these include:
• Developmental delay
• Intellectual disability
• Low muscle tone
• Poor gross and fine motor skills
• Feeding difficulties in infancy
• Vision and hearing problems
• Sleep disturbance
• Behavioural difficulties

For children with SMS, early intervention can help manage symptoms, support better outcomes, and help them to achieve their full potential. Ongoing support from health professionals such as Accredited Exercise Physiologists can help people with SMS stay healthy and lead full lives.


People with SMS have been found to demonstrate behaviours with food that can lead to obesity. A study published in 2015 found these behaviours are like those of people with Prader Willi Syndrome. They include preoccupation with food and a marked decrease in feelings of satiety (fullness after eating), regardless of how much food is consumed.

These food-related problems can start in infancy, but this study found adults and children aged 12–18 years demonstrated the most significant problems with overeating and food-related behaviours. The researchers concluded that treatments used to prevent obesity in people with PWS could be beneficial for people with SMS. This includes regular physical activity.

Preventing obesity is vital, because obesity in childhood has been shown to negatively impact physical wellbeing. It is associated with conditions that affect many body systems, including the heart and blood vessels, lungs, nervous system, and bones, muscles and joints. Importantly, childhood obesity can also affect social and emotional wellbeing and self-esteem.

Children who are overweight or obese are more likely to remain that way into adulthood and are more prone to developing diabetes and cardiovascular diseases at a younger age.

Adults who are obese are at greater risk for developing several health conditions and chronic diseases, with risk rising with the increase in excess weight.

Along with health risks, obesity can hamper your ability to perform everyday tasks like climbing stairs or putting on your shoes and socks. These issues can impact an individual’s independence and their ability to participate at home, school, work and in their community.


On the upside, regular physical activity is linked with improved weight management, lower blood pressure, and reduced risk of many problems, including type 2 diabetes, heart attack, and some cancers. Significantly, regular physical activity can boost mood, increase energy, and enhance sleep.

Although more research is needed into exercise specifically for people with SMS, studies on exercise for people with PWS have shown most long-term exercise programs result in reduced body mass and better physical performance.

Regular exercise can support better health, function and independence in people with SMS, allowing them to participate in activities they enjoy and lead a satisfying life.


An Accredited Exercise Physiologist can create a program designed to suit each individual’s needs and goals. This will usually involve different types of exercise, including:


Aerobic activities like cycling, walking, swimming, dancing, or boxing promote a healthy heart, lungs and circulation. Along with resistance exercise, aerobic activities can help offset the energy input from food. It also activates release of the ‘feel good’ hormones that lift mood.


Low muscle tone is a key characteristic of SMS. This can lead to overall weakness and difficulty with co-ordination and gross and fine motor skills. Resistance exercise using either body weight, bands, dumbbells or other weighted objects can help build muscle strength and endurance and support bone health.


People with SMS tend to have a wide-based walking pattern and may have flat feet and short toes. Additionally key symptoms of SMS such as muscle weakness and obesity can also lead to issues with balance. Gait (walking) and balance exercises might therefore be prescribed to optimise an individual’s walking pattern and improve their balance.


People with SMS are prone to developing spinal curvature (called scoliosis) and exercise might be recommended to maintain spinal flexibility and good posture.


People with SMS usually need ongoing support to make positive health choices. Building caregiver capacity helps ensure health goals are met and reduces the need for continued support from professionals.


SMS causes a range of issues that can make getting adequate physical activity challenging. For example, intellectual disability can mean individuals with SMS have difficulty understanding why physical activity needs to be part of their regular routine. Additionally, some individuals with SMS can also exhibit behaviours of concern, such as impulsivity and explosive outbursts. In this circumstance, it is recommended to seek the guidance of an experienced exercise professional who has experience with SMS or who can work within the scope of an individual’s behaviour support plan.

Individuals with SMS may have issues, including low muscle tone and heart and kidney defects, that can make some types of exercise unsuitable. These complex needs mean getting guidance from an Accredited Exercise Physiologist is vital before starting an exercise program.

Click here to find an accredited exercise physiologist near you.

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Written by Amanda Semaan and Kara Foscholo. Amanda and Kara are Accredited Exercise Physiologists and Co-Directors of Active Ability, whose mission is to support people with disability to achieve optimal independence, health and quality of life.