Diagnosis and Initial Treatment
A 24-year-old woman from Cardiff, Caitlin Leggett, was diagnosed with acute myeloid leukaemia (AML), an aggressive cancer affecting white blood cells, in April 2025. The only initial symptom was a persistent rash. Following chemotherapy, she entered remission and subsequently underwent a stem cell transplant. However, in May 2025, Caitlin was informed that the cancer had returned and that curative treatment options within the UK were unlikely.
Current Treatment Pursuits and Financial Challenges
Currently, Caitlin is seeking potentially curative treatment abroad, most likely in the United States, where the treatment and associated expenses could total approximately £500,000.
Impact on Twin Sister
Caitlin’s identical twin sister, Grace, expressed the emotional difficulty of the situation.
"We're only 24 - nobody expects this to happen... Being twins as well, you're not supposed to have one twin not be there,"Grace said. Caitlin added,
"It's unthinkable. We've gone through life together and I don't want our story to end here."
Discovery of Identical Twin Status
The sisters, who have always been close and lived together during university, only learned they were identical twins following Caitlin’s diagnosis. Previously, they were believed to be fraternal twins due to developing in separate amniotic sacs. However, during Grace’s assessment as a potential stem cell donor, doctors identified that their genetic markers were identical.
This revelation complicated Caitlin’s treatment, as Grace was no longer eligible to donate stem cells due to their nearly identical DNA.
Background and Initial Symptoms
Before her illness, Caitlin had planned to join the Army and train as an intelligence officer after graduating in July 2024. She had a medical assessment scheduled for April 2025, but in March, she developed a rash that did not respond to pharmacy creams. Blood tests led to her being referred to the Teenage Cancer Trust unit at the University Hospital of Wales in Cardiff the next day, where she realized the severity of her condition.
Treatment Timeline and Relapses
While awaiting an alternative donor from the register, Caitlin achieved remission in May 2025 after two months of chemotherapy. However, in August 2025, the cancer returned to her skin. She participated in a clinical trial in Manchester involving menin inhibitors, which successfully induced complete remission before a planned stem cell transplant. Yet, a week prior to the transplant date in December 2025, the cancer reappeared on her skin.
Despite this, Caitlin proceeded with the transplant after receiving additional full-body radiotherapy and was declared in remission again in January 2026. She was scheduled for monthly bone marrow monitoring for three months to detect any recurrence, with plans to reduce testing frequency to quarterly from March 2026. Caitlin expressed concerns about this reduction, persuading her consultant to add an extra test in May 2026. This test revealed that the leukaemia had returned.
Understanding Acute Myeloid Leukaemia
According to the NHS, symptoms of AML can include pallor, fatigue, breathlessness, unusual bruising or bleeding, and unexplained weight loss. Caitlin, however, experienced none of these symptoms aside from the unusual rash, which can also indicate blood cancer.
Stem Cell Donor Search and Family Testing
Upon learning that treatment would involve a stem cell transplant to replace cancerous cells with healthy donor cells, Caitlin’s entire family was tested to identify a suitable match. Blood cancer and blood disorder charity DKMS reports that over 2,000 people annually in the UK require blood stem cell transplants, yet only 7% of the eligible UK population are registered as potential donors.
Ongoing Trials and Prognosis
Since May 2026, Caitlin has participated in a drug trial for Bleximenib and is awaiting results to determine her response. Her medical team has indicated an alternative drug trial option if this treatment is unsuccessful but has advised that these therapies are not curative. Additionally, Caitlin has been informed that a second stem cell transplant is not feasible in the UK. Doctors have estimated that her current treatment plan may extend her survival by approximately six months.
Seeking Treatment Abroad and Fundraising Efforts
Consequently, Caitlin is exploring curative treatment options abroad, including specialised leukaemia treatment in the United States or CAR-T cell therapy, a form of immunotherapy, in China or Singapore. Both options involve costs amounting to hundreds of thousands of pounds. The sisters have established a fundraising page aiming to raise £500,000 to cover treatment and travel expenses.
"It's incredibly difficult to think about,"Caitlin said.
"At 24, I always assumed I had my whole life ahead of me. There are so many things I still want to do, places I want to see and memories I want to make with the people I love. I don't want to miss out on the future we always thought we'd share together."
