French scientists have discovered a new blood type in a woman from the Caribbean island of Guadeloupe, France’s blood supply agency announced Friday.

The woman is the only known carrier of a new blood type, dubbed “Gwada negative,” the French Blood Establishment (EFS) said. The discovery was made 15 years after researchers received a blood sample from a patient who was undergoing routine tests ahead of a surgery.

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This woman “is undoubtedly the only known case in the world,” he said, adding: “She is the only person in the world who is compatible with herself.”