Symptoms include mild to moderate intellectual disability, delayed speech and language skills, sleep disturbances, and behavioural problems.
"Living with a person with SMS can be very challenging, and bit by bit we were exhausted," Ms Fraser said.
"We never slept, Lachlan's increasing frustration involved him becoming aggressive and difficult to manage.
"We never went anywhere and no one came to visit – it was a lonely existence."
An in-home support worker helped not just Lachlan, but the family as well, acting as the "rock".
However, by the time he was 12, Lachlan's behaviour had got to the point where the family could not cope.
He was accepted into Kingsdene, a boarding school for students with disabilities and used a respite bed on the weekend.
Lachlan thrived in care, and Ms Fraser's role changed from one of physical carer to advocacy.
"Sometimes this role is harder," she said.
"You are helping people understand how to look after your loved one – expecting them to take as much care as you would and frequently being disappointed."
It was during this period that Ms Fraser decided to return to the workforce, inspired by her experience with her son to begin working in education.
"I help support kids with a variety of additional support needs including autism and intellectual disability," she said.
"Caring for Lachlan gave me skills to help others, he taught me patience, he taught me to look for communication behind behaviour and to strive to help others understand that and how best to help them."
She also sought support from the Northern Sydney Local Health District's Carer Support Service.
"They have helped me to navigate through the maze of government and non-government agencies to secure the help and support that Lachlan requires," Ms Fraser said.
"It is a constant battle and part of a caring role that is often overlooked."
NSLHD Carer Support Service manager Barbara Lewis said it was great to help people like Ms Fraser.
"Our aim is to help support wonderful people, like Kate, as they care for their loved one in what are often difficult circumstances," Ms Lewis said.
"Being a carer is a huge commitment with a range of responsibilities and that can be overwhelming for a lot of carers whether they be mums, dads, grandparents, children, partners or friends."
Ms Lewis hoped people used the week to acknowledge the work that around 120,000 careers in the district do.
"Carers Week is an ideal time for everyone to recognise and respect the important work that carers do every day of the year," she said.
"We provide free guidance and support to carers in our region. Anyone who is a carer in our community and wants more information should visit our website nscarersupport.com.au or call 9462 9488."
Picture: Carer Kate Fraser and son Lachlan