Dementia as a toddler: UK 2-year-old dies after developing a rare form of the illness

Two-year-old Mirryn Cunningham has died in the UK after struggling with a rare form of childhood dementia.

"No pain any more. No medication. No drips. No oxygen. Just Mirryn," mum Vicky told the BBC.

The illness, known as Batten disease, meant she could not see or walk properly, nor eat food on her own.

"She fought hard for a long time now," Vicky said.

There is no cure for Batten disease, the BBC reports, and only about six children in the UK are born with it every year.

Mirryn spent the last two months of her life at the Children's Hospice Association of Scotland, where she died on Sunday (local time).

"She was getting her favourite story and she was being cuddled by mum and she just put her head on me and she took her last breath," Vicky told the BBC. "A big massive breath and that was her."

Vicky described her daughter as "miracle Mirryn".

"She fought hard and she earned her name miracle, she passed away in the most loving way with her family around her," a Facebook post on the page 'Team Miracle Mirryn' says.

According to the National Institute of Neurological Disorders and Stroke website, children with Batten disease often appear healthy and develop normally before they begin to show symptoms.

"Common symptoms for most of the forms include vision loss, seizures, delay and eventual loss of skills previously acquired, dementia, and abnormal movements."

The website says children may develop personality and behaviour changes.

"Over time, affected children may suffer from worsening seizures and progressive loss of language, speech, intellectual abilities (dementia) and motor skills."