I won’t have any more children, because my first-born has dementia

The parents of a girl with ‘childhood dementia’ have revealed why they felt they had no choice but to terminate their much-wanted second pregnancy after discovering their unborn child also has the disease. 

Leni Forrester, now two, was born seemingly healthy to parents Emily, 33, and Angus, 35, from London. 

But when a close family member underwent genetic testing six months ago, their lives changed forever when results showed the family carried a recessive gene which can cause Sanfilippo syndrome, a rare genetic disorder dubbed childhood dementia.

The degenerative disease causes children to gradually lose all the motor skills they’ve learnt – such as walking, talking and eating – by the time they reach their teenage years. 

There is currently no cure for the disease, and most of the children diagnosed with the devastating condition die by the time they reach their mid-teens. 

The chances of both parents carrying the gene are slim, but after noticing that Leni was already exhibiting some of the classic symptoms – including speech delay, hearing difficulties and unusually bushy eyebrows – Angus also underwent testing.

Thankfully, the test came back negative and the couple began trying for a second child. 

But just weeks later, the parents were informed the test results were wrong, triggering the ‘most intense grief’ imaginable. 

Leni was diagnosed with the condition in October 2025, and just two weeks later, the couple found out that they were pregnant. 

Ms Forrester said: ‘We knew this pregnancy would either be the very best or very worst possible news. 

‘Navigating the heartbreak of Leni’s diagnosis and our new world as parents to a child with very complex medical needs, as well as facing all the challenges any parents faces of having a toddler and trying to give her the best life possible.’

Ms Forrester had to carry the foetus for three months before it could undergo genetic tests in utero, which would reveal whether the baby would have the condition. 

‘We tried to detach from the pregnancy and not get our hopes up – but as there was a 75 per cent chance that the baby would be unaffected, we couldn’t help but cling on to that hope,’ she added. 

‘We desperately wanted to grow our family and want our future children to know Leni as she is today, and for her to know them.’

But sadly, in utero testing revealed their growing baby would also be born with Sanfilippo syndrome. 

With this knowledge, the couple felt they had no other option than to terminate the pregnancy, and focus all of their efforts on Leni. 

Ms Forrester said: ‘With no treatment options, no cure, a catastrophic prognosis and poor quality of life – how could we knowingly bring another child into the word with Sanfilippo syndrome? 

‘We made the impossible decision to end the pregnancy, and I had a surgical termination a few days before Christmas.

‘It was the most heartbreaking and difficult decision we have ever had to make. But we knew deep down there was no choice.’ 

She added: ‘Unless you have received a catastrophic diagnosis like this for your child you cannot imagine the heartbreak and the devastation we felt in this moment. 

‘I now truly know what it feels like for your heart to be ripped out of your chest.’  

Whilst there is currently no known cure for the neurodegenerative disease that is estimated to affect one in 200,000 births, a clinical trial for a potential treatment is expected to begin in the US later this year.

Leni’s parents are now calling on the UK Government to help fund the research so the trial could also include children like Leni. 

Ms Forrester said: ‘With Leni’s condition, weeks and months matter as toxic waste builds up in her tiny body every single day and the damage cannot be reversed once its done. 

‘Time is working against us. It’s now or never for Leni.’ 

Despite her condition, Leni’s parent’s describe their toddler as ‘a bundle of energy’ who loves to make people laugh. 

But whilst they celebrate each new developmental milestone she hits, they know it’s a race against time to get treatment. 

‘Our beautiful child who we are watching develop into an incredible little person and getting a glimpse of who she might become, will lose the ability to walk, talk, swallow laugh, eat, and eventually her life to this condition,’ her mother explains.  

‘The difference between her getting access to this treatment now and in a years time could be the difference between a potentially near-normal life and a significantly shortened life with the most severe mental and physical disabilities you can imagine.

‘I cannot imagine a more cruel, catastrophic condition with a worse impact on the child or the families and friends who love them. 

‘This is her only hope.’

The disease is inherited when both parents carry one copy of a defective gene that leaves the body unable to break down a substance called heparan sulfate – or cellular waste.

Because the body can’t break down this toxic waste, it builds up in the brain and other organs, killing off cells. 

Children with Sanfilippo syndrome also tend to have prominent, thick eyebrows and coarse hair, as well as full lips and nose. 

In addition to speech and developmental delays, early symptoms include fast breathing after birth, larger head size, excessive body hair and sleep disturbances.  

Leni’s parents have already raised more than £360,000 in a bid to get Leni and other children access to potentially life-saving treatment. 

The treatment works by delivering a missing gene into the patient’s bloodstream via stem cells, but getting started on the clinical trials requires a huge amount of funding. 

They are also calling for newborn screening to help detect rare genetic conditions earlier and for more funding to accelerate treatments.

While conditions like Sanfilippo syndrome affect a relatively small number of children, Mr Forrester says that taken in aggregate, ‘rare’ diseases have a much broader impact than many realise.

‘When you group all these rare conditions together, they suddenly don’t become that rare.’