An egg from Loló Suárez and a sperm from Eduardo Agraso fused one day in 2010 and formed a single cell with the same DNA, from which two identical twin sisters ended up being born: Cayetana and Celia. Both are now 12 years old, they enjoy swimming at the beach in their town—Portosín (A Coruña)—and share the same genetic mutation, but Celia has practically no symptoms, while Cayetana's muscles are rapidly turning into bone. The girl herself asked a year and a half ago to have both of her legs amputated, since they had already become stone, to make your life easier. The pediatric Federico Martinón Torres She co-leads the medical team that works against the clock to understand why the disease affects one sister and respects her twin. The secret to curing the pathology could be hidden in Celia, or at least a clue. “It seemed like a perfect experiment: two identical people, one sick and the other healthy, but it is not being so obvious,” laments Martinón.