The story started with a 27-year-old patient with a conditions known as focal segmental glomerulosclerosis (FSGS), which causes scar tissue on the part of the kidney that does the actual filtering of waste from the blood, leading eventually to kidney failure. The man received a kidney from his sister, but within days signs of his FSGS began to manifest themselves the new kidney, posing life-threatening complications. The new kidney had to come out--but, doctors thought, why discard an otherwise perfectly good organ when there are so many people on the waiting list for donated kidneys.