Cancer Uncovers Hidden Identical Twin Secret

Twin sisters Caitlin and Grace Leggett, aged 23, from Cardiff, learned they are identical twins after Caitlin was diagnosed with acute myeloid leukaemia (AML) in March 2025. The sisters had always believed they were fraternal, a notion supported by their parents based on their development in separate amniotic sacs.

Caitlin's journey began with a persistent rash in March 2025, leading to her AML diagnosis on April 4, 2025, at the University Hospital of Wales. Initially, Grace was identified as a potential stem cell donor, having registered years prior. However, doctors discovered their identical DNA meant Grace could not donate, as a transplant requires the recipient's body to recognise donor cells as foreign.

Caitlin underwent chemotherapy, with a stem cell transplant initially planned for August 2025. When Grace could not donate, a search for an alternative donor commenced. The transplant was postponed due to the leukaemia spreading to Caitlin's skin, leading her to participate in a clinical trial in Manchester. Further setbacks occurred when a new donor withdrew and the cancer returned to her skin just a week before a second transplant attempt in December 2025. This necessitated full-body radiotherapy before the transplant from an anonymous donor finally took place in December 2025, proving successful.

Caitlin's treatment continues as she participates in a new drug trial. Both sisters have become passionate advocates for stem cell donation, highlighting that only 7% of eligible individuals in the UK are registered donors, despite over 2,000 people annually needing a transplant. They emphasize the life-changing impact of donation and its relative ease.