A five-year-old girl from Essex, Holly Nayler, suffers from CLN2 Batten disease, a rare and fatal childhood dementia. This disease affects fewer than 50 children in the UK. It slowly takes away her ability to walk, talk, see, and eat on her own. Holly experiences up to 200 seizures a day, with a record 187 seizures in 24 hours. Holly’s parents, James and Lauren Nayler, say she had no early warning signs. She walked and spoke early and passed health checks. Problems began just before her third birthday when seizures started. After genetic tests, Holly was diagnosed with CLN2 Batten disease on March 26, 2024. James Nayler said, "Your world just stops. You’re trying to take in what they’re telling you but at the same time, your mind is going a million miles an hour." The disease is caused by a genetic mutation that blocks an important enzyme. Without this enzyme, waste builds up in brain cells, causing quick brain damage. Most children lose movement, speech, sight, and need feeding tubes by age six. Life expectancy is usually between six and 12 years. Holly still goes to school five days a week. Some days are good; others are hard. "Sometimes she’ll survive all day and other times we’ll get a phone call saying she’s not coping well," said James. Holly’s vision is unclear, and seizures worsen despite treatment. James calls her "a really cheeky, happy little girl" who loves Paw Patrol and dinosaurs. Holly gets an enzyme drug called Brineura through brain surgery every two weeks at Great Ormond Street Hospital. The four-hour infusion slows the disease but does not cure it. The family travels up to 13 hours round trip for treatment. Brineura costs more than £500,000 per child a year. NICE tried to stop recommending the drug after the initial access period ends, but after an appeal, the agreement continues until June 2026. Children already on treatment can continue, but future access is uncertain. James said, "These children deserve a life and they deserve a life which keeps as many of their skills and functions for as long as possible. This drug is the only one in the world that can do that." Holly’s story highlights the urgent need for awareness and support for children with rare dementias in the UK.