British two-year-old diagnosed with rare childhood dementia had no 'obvious signs' of illness

Until seven months ago, two-year-old Leni Forrester had been an image of perfect health.

According to her parents, Emily and Angus Forrester, the British toddler had been born 'full of love and life', and presented no indication of something being wrong behind the scenes.

One day, however, a close relative of Leni's underwent a genetic test before finding out that they carried a gene for a rare disorder known as Sanfilippo.

The metabolic condition is caused by a singular gene defect which triggers a deficiency in the enzymes needed to break down a complex sugar called heparan sulfate. Over time, Sanfilippo causes severe, progressive brain damage.

Though doctors ruled it unlikely that Leni would suffer any variation of the devastating condition, Emily and Angus sought further investigation, only to be dealt the news they'd dreaded most.

Emily and Angus claim Leni showed no signs of ill health prior to her diagnosis (GoFundMe)

Their beautiful baby girl was diagnosed with Sanfilippo Syndrome Type B (MPSIIIB) a week prior to her second birthday.

This specific strain of the heartbreaking syndrome causes severe intellectual disability, hyperactivity, and speech delays, all of which typically appear during early childhood, or ages 1-6.

Tragically, it's a condition without a cure.

This hasn't stopped Leni's doting mother and father from setting up a GoFundMe page, through which they hope to accumulate enough money to provide their daughter with life-saving treatment.

"Sanfilippo Syndrome is unimaginably cruel," Emily wrote on the page description. "Children develop relatively ‘normally’ with no obvious symptoms until they are around two years old.

The toddler requires critical care (GoFundMe)

"Then over a short amount of time they lose all skills once learned, experience severe behavioural challenges, extreme hyperactivity, insomnia that can last for days, seizures, a total loss of cognitive and motor function, and a premature death in their early to mid-teens, as well as many other horrific symptoms," she continued.

"Sanfilippo is relentless and leaves nothing untouched."

A clinical trial for Sanfilippo Syndrome Type B, costing £5.5m per patient, will begin in the US towards the end of the year. Patients will have a permanent port fitted into their brains that replaces the enzyme they're born without, flushing the body with it through weekly, life-long treatment.

Sadly, however, UK patients can't currently be included - a reality that prompted Emily and Angus to call upon the British government to fund the research.

Another possibility for Leni would be gene therapy developed by UK-based Professor Brian Bigger, which hasn't yet reached clinical trials, and cannot without a considerable amount of funding.

Leni's parents set up a fundraiser for critical treatment (GoFundMe)

Doctors have ruled, however, that Leni must receive some form of critical care within the next five months, before her third birthday - and even this could still see the tot losing a number of basic skills.

"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 it is done," Emily explained. "Time is working against us.

"The difference between her getting access to this treatment now and in a year's 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.

"It’s now or never for Leni."

She and Angus' fundraiser currently stands at just over £360,000.