11-Year-Old London Girl Becomes First UK Patient to Receive Gene Therapy for Rare Sight-Robbing Condition

Catherine L’Estrange, an 11-year-old from London, has become the first patient in the UK and the second globally to receive a pioneering gene therapy for Bardet-Biedl syndrome (BBS). The hour-long procedure, performed at St Helier Hospital in March 2026, involved injecting healthy copies of the BBS10 gene into her retina to halt progressive blindness. While BBS typically robs patients of their sight by their late teens or early twenties, early feedback from the trial has shown promising signs of improved vision in dim light.

Gene therapy procedure for BBS

• ▪Catherine L’Estrange, an 11-year-old girl from North Acton, London, became the first patient in the United Kingdom to receive a pioneering gene therapy for Bardet-Biedl syndrome.
• ▪Surgeons treated one of Catherine L’Estrange's eyes by removing the jelly inside the eye and injecting healthy copies of the BBS10 gene directly into the retina.
• ▪The hour-long gene therapy procedure, developed by biotechnology company MeiraGTx, was performed on Catherine L’Estrange at St Helier Hospital in March 2026.

Bardet-Biedl syndrome characteristics

• ▪Bardet-Biedl syndrome causes small cells in the retina to die, typically leading to blindness by a patient's late teens or early twenties.
• ▪Bardet-Biedl syndrome is a rare genetic condition caused by mutations in one of 20 different genes, affecting approximately one in 100,000 births in the United Kingdom.
• ▪Beyond vision loss, Bardet-Biedl syndrome can manifest with kidney problems, learning difficulties, obesity, and occasionally extra fingers or toes.

Vision monitoring after treatment

• ▪Consultant eye surgeon Neruban Kumaran reported that early feedback is positive, with some patients stating their vision in dim light has improved, though full results will take years to determine.
• ▪Following the gene therapy, patients undergo clinic visits and sight tests, including reading from a chart and identifying different shades of colors.

Patient family experiences

• ▪Reverend Timothy L’Estrange, Catherine's father, stated that the family focused on developing her independence and resilience in preparation for her progressive loss of night, color, and peripheral vision.
• ▪Catherine L’Estrange was diagnosed with Bardet-Biedl syndrome at a few weeks old, which is highly unusual as most children with the condition are not diagnosed until primary school.

Clinical trial patient eligibility

• ▪The gene therapy is designed specifically for patients with a mutation in the BBS10 gene, which is one of the most common mutations among Bardet-Biedl syndrome patients.
• ▪Prior to Catherine L’Estrange's procedure, only one other person globally—a 17-year-old girl from Canada treated in August 2025—had received the gene therapy.
• ▪St Helier Hospital collaborated with experts at Great Ormond Street Hospital and Moorfields Eye Hospital to identify eligible patients using genetic tests.