Leni Forrester, aged three, has been diagnosed with Sanfilippo syndrome, a rare neurodegenerative condition that causes childhood dementia. Her parents, Angus, 36, and Emily Forrester, 34, are fundraising to start an enzyme replacement therapy trial in the UK, after a similar trial in the US yielded promising results before being cut short due to lack of funding.
Early signs and diagnosis
Leni's parents did not have concerns when she was 15 months old. Early signs, such as severe hyperactivity, sleep disturbances, and a speech delay, were initially attributed to other causes like autism, ADHD, or the hearing aids Leni wears. Other symptoms, including a low nose bridge, bushy eyebrows, a large head, ear infections, and diarrhoea, seemed unrelated and were linked to normal childhood quirks.
Alarm bells began to ring after a family member's positive gene test for Sanfilippo syndrome. After six months of investigations, a geneticist fast-tracked a rare 'rapid response test' reserved for the most urgent cases. The family received the devastating news on a video call, where consultants told them there was no cure and no treatment.
Impact on the family
Sanfilippo syndrome affects around one in 70,000 births and means Leni cannot produce a vital enzyme needed to break down a complex sugar molecule, leading to childhood dementia. Without intervention, Leni will gradually lose the ability to walk, talk, and play before the illness takes over. Most children with the condition die before their 18th birthday.
Emily described the feeling as "primal," saying, "Your role as a parent is to protect your child, and suddenly your whole future for your family, for your child, everything that you had imagined in one 15-minute conversation, gets absolutely flipped." The family has moved from their south London flat to live with Emily's dad in Kent to give Leni more outside space, and Emily's sister has moved from Australia with her six-month-old twins to spend time with them.
Fight for treatment
Gus and Emily are fundraising for a trial in the UK after discovering an enzyme replacement therapy trial in the US, which infuses the body with the enzyme weekly, yielded promising results before it was cut short. Gus said, "The kids were responding really, really well, and then it ran out of funding and then just got put on the shelf."
In Australia, a child with Sanfilippo received an experimental gene therapy infusion at 12 months old, a different one-dose treatment. Now nine, Tilly Page's family says she has developed typically. Gus and Emily feel distraught at what could have been achieved in the UK had funding been available.
Gus said, "The cures exist, the treatments exist, but because of funding and red tape and bureaucracy, it basically just hasn't got to a point. If you treat this at birth or in the first year of life, they can leave a near-normal life, completely normal, as a normal child."
Broader context and calls for action
Leni is the only child under five in the UK currently diagnosed with type B. Many parents spend years searching for answers, known as the 'diagnostic odyssey'. Gus and Emily want prenatal testing to become routine, as British clinics currently only test for 11 health conditions at the 20-week scan.
More than 140 conditions cause dementia symptoms in children, yet the term is not recognised in UK policy. Professor Simon Jones, consultant in paediatric inherited metabolic diseases at Manchester University NHS Foundation Trust, wrote, "The disparity is stark — only seven FDA-approved drugs exist for childhood dementia compared to 51 for childhood cancer, and those seven drugs only help about 10% of diagnosed children."
Gus and Emily want Andy Burnham to include childhood dementia in his £48million dementia strategy, which currently encompasses adults. After securing a trial, they hope to create a charity so no other family has to navigate childhood dementia alone. Emily said, "It wasn't really a decision. You will do anything you can for your kid. It doesn't matter how uncomfortable it feels."
A Department of Health and Social Care Spokesperson said: "Neurodegenerative conditions such as Sanfilippo syndrome have a devastating impact and our thoughts are with Leni and family. We are making sure patients with rare diseases get a definite diagnosis faster, while improving access to specialist care, treatment and drugs."
