An 11-year-old girl from London has become the first patient in the United Kingdom to receive an innovative gene therapy aimed at treating Bardet-Biedl syndrome (BBS), a rare genetic disorder that causes progressive vision loss in children. The procedure, performed at St Helier Hospital in March, involves injecting healthy copies of a gene directly into the retina to preserve or potentially improve vision.

Catherine L’Estrange, diagnosed with BBS as an infant, has experienced a gradual decline in sight, including night blindness, loss of color perception, and narrowing of peripheral vision. Her father, the Rev Timothy L’Estrange, said the family had previously been told that gene therapy treatments were likely years away and might only become available after Catherine had lost her vision entirely. The recent availability of the treatment, therefore, came as a surprise and a source of hope.

BBS affects roughly one in 100,000 children in the UK and is caused by mutations in any one of 20 different genes. Alongside vision loss—typically resulting in blindness by the late teens or early twenties—the syndrome can lead to kidney problems, learning difficulties, obesity, and, in some cases, extra fingers or toes. The gene therapy, developed by biotechnology firm MeiraGTx, was administered during an hour-long operation involving the removal of the vitreous gel inside one eye and injection of the therapeutic gene into the retinal cells.

Neruban Kumaran, a consultant eye surgeon at Epsom and St Helier University Hospitals NHS Trust, explained that delivering a healthy gene copy aims to rescue retinal cells from degeneration, with the goal of stabilizing or improving vision. Only one of Catherine’s eyes was treated initially as a precaution in case of any adverse effects. Medical teams are monitoring her progress, alongside another younger child who recently underwent the same treatment.

This treatment has been offered to very few patients globally, with only one other known case—a 17-year-old girl from Canada—having received the therapy at St Helier Hospital in August of the previous year. Her family expressed cautious optimism, hoping the therapy will become a transformative option for children with certain genetic subtypes of BBS worldwide.

While some early reports from patients and families have indicated improvements in vision, particularly under dim lighting conditions, experts emphasize that it will take several years to fully assess the long-term efficacy of the treatment. Kumaran noted that although the gene therapy is unlikely to restore perfect vision, its potential to halt or slow decline could significantly improve patients’ quality of life and independence, especially given the absence of alternative treatments.

Efforts are underway at St Helier Hospital, in collaboration with Great Ormond Street and Moorfields Eye Hospitals, to identify additional children eligible for the therapy through genetic testing that determines the specific gene mutations involved in their cases.

Mat Shaw, chief executive of St George’s, Epsom and St Helier Hospitals Group, highlighted the emotional impact on families facing progressive childhood blindness and expressed pride in the team’s role in pioneering a treatment that offers hope to those affected by this devastating condition.