Two sisters aged just six and 10 were among the youngest people in Britain to have been diagnosed with dementia, their parents have revealed.
Emily and Sarah Bushaway both developed Niemann-Pick disease type C, a rare genetic disorder, often known as childhood Alzheimer's, that affects only hundreds of people worldwide.
Emily was diagnosed with the condition at the age of six. Seven years later, her younger sister, then aged 10, began showing symptoms. Parents Mark and Lisa Bushaway, both 48, became full-time carers for their daughters as they lost the ability to walk, talk and write.
They have spoken out to raise awareness of the condition after Emily died aged 21.
"It's such a cruel disease, one of the worst illnesses I have ever heard of. It's robbed us of so much," Lisa told the Mirror.
"If anyone developed dementia, we expected it to be me and Mark, when we reached old age. We never expected our young girls to need constant care."
Symptoms of the disease typically begin to show in childhood and include coordination problems, poor muscle tone, and lung and liver disease. Sufferers often experience a progressive decline in intellectual function.
Emily's parents first took her for tests after she began repeating herself and struggling to remember friends' names. They were initially told she had ADHD, which affects concentration, but neurologists at Great Ormond Street Hospital in London later carried out tests and diagnosed Niemann-Pick disease.
Mark and Lisa both carry the gene for the disorder, giving their children a one in four chance of developing it. "I used to have a faith, but having two children with this disease has stopped that," said Lisa, from Letchworth, Hertfordshire. "With one, you think you can manage, and they've been sent by God for you to look after, but two? That's simply too cruel."
Sarah, now aged 19, has reduced life expectancy. Emily died at a hospice in Oxford in May 2016 after a nurse mistakenly threw away part of her breathing tube. A coroner last month ruled Emily's death was partly contributed to by neglect by the hospice, where she had been staying for a few days as her bedroom was redecorated.