There is no doubt that caring for a baby is a challenging experience – but one which is also cherished by proud parents.

Imagine, though, that your baby is 15 years old.

That is the reality for the family of Toby Williamson, who has a mental age of nine months - who care for Toby at their home in Alcester, Warwickshire.

Toby was born full term after a normal pregnancy, but it soon became apparent that he was not feeding well, was sleepy and passive and had poor eye control. Tests established that he had abnormally low muscle tone, with global developmental delay leading to severe learning difficulties and a visual impairment.

Toby's subsequent medical history has included regular ear infections and burst ear drums (upsetting his hearing, balance and learning); reflux, leading to hospitalisation for dehydration and subsequent medication; a squint, corrected by surgery in 2004; a diagnosis of Autism Spectrum Disorder in 2010; and many genetic tests - none of which have yet found a cause for his condition.

His family are now hoping that the nationwide 100,000 Genomes Project may provide that elusive answer, after Toby became the 1,000^th recruit to the initiative in the West Midlands.

“Toby is 15-years-old but has the learning age probably of about a nine-month-old and the physical ability of just over a one-year-old,” said mum Charlotte. “That will give you an idea of the needs he has and the type of help and support we give him.

“He’s a baby, basically, in a teenager’s body. He relies on us totally for all of his personal care and all of his needs have to be met. He has very limited communication, which is all non-verbal.

“He can walk, but not very far, he has no reason to understand why he has to walk from A to B, and he’s incredibly demanding in terms of day to day care because he has no understanding of danger. You constantly have to listen out for him, be aware of things for him and think for him.”

Doctors at Birmingham Women’s Hospital, where Toby has regular genetic checks, suggested that the family take part in the 100,000 Genomes Project.

The hospital is one of 18 across the region, led by University Hospitals Birmingham, which have come together to form the West Midlands Genomic Medicine Centre (WMGMC) – one of 13 such collaborations in England which are delivering the project.

The aim is to collect and sequence 100,000 whole genomes, your body’s unique genetic code, from patients with rare diseases and their families as well as cancer patients to enable doctors to understand the conditions better and, going forward, develop patient-specific personalised care.

“Having the 100,000 Genomes Project is brilliant,” added Charlotte, a part-time PE teacher. “If someone could finally tell us what caused Toby to be the way he is, that would be wonderful. It wouldn’t change his life but it would give us some sort of closure.

“But if we don’t personally get an answer, it could still help someone else in the future and that’s why we do it, because I wouldn’t wish our life on anybody.

“There may be some answers out there that could not only help other children like Toby but potentially, for our daughter, we would love to be able to free Rosie from the concerns about her children or her children's children being another Toby.”

Charlotte, her self-employed project manager husband, Jay, and 17-year-old Rosie all help with Toby’s day-to-day care, which dominates all aspects of their lives.

Rosie, a talented sailor who has competed at national and international level, is hoping to go to university after her A-levels, however, and although Charlotte employs a number of carers to help out, his parents worry about Toby’s future.

"As he grows he is becoming harder for my husband and me to manage,” said Charlotte. “As he gets older we won’t be able to physically lift him, and we’re older parents anyway.

“We have hopes and aspirations for Toby and where he will go in the future but whether there is funding for that is uncertain because, like all these things, the money is drying up.

“Hopefully he will go on to some sort of residential college and some kind of residential living because he is just going to become too difficult for my husband and I to manage.

“But the good thing about Toby as a person is that he’s happy. I think that’s so important because there are many children who lead normal lives but are unhappy. From our point of view that makes all the hard work of looking after him more rewarding, otherwise it would be very difficult.

“It really is a tough life as the parent of a child like Toby, just walking around and trying to do all the things that people do normally. It can be quite an isolating world.”

Dr Jenny Morton, Consultant Clinical Geneticist at Birmingham Women’s Hospital, said: “Patients, like Toby, are absolutely at the heart of this project.

"Genomics is vital to the future of healthcare and this project is ensuring the NHS is providing the latest advances in diagnosis and treatment for its patients. The contributions of people like Toby and his family are helping to build the future of healthcare across the country.”