How did a leukaemia diagnosis reveal twin sisters were identical?

A leukaemia diagnosis for Caitlin Leggett led doctors to discover that she and her twin sister Grace were actually identical, not fraternal, due to their matching DNA markers.

Why couldn't Grace Leggett donate stem cells to her sister Caitlin?

Grace could not donate stem cells because she and Caitlin are identical twins. A successful transplant requires the recipient's body to recognize donor cells as foreign, which would not happen with near-identical DNA.

What is the importance of stem cell donation according to the Leggett twins?

The Leggett twins, Caitlin and Grace, are advocating for stem cell donation, emphasizing that it can save lives and that only a small percentage of eligible people are registered donors.

Home / Health / Cancer Uncovers Hidden Identical Twin Secret

Cancer Uncovers Hidden Identical Twin Secret

24 Feb

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Summary

Leukaemia diagnosis revealed twin sisters were identical, not fraternal.
Identical twins' DNA prevented one from donating stem cells.
Sisters now advocate for stem cell donation awareness.

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.