When their daughter Kate (Sofia Vassilieva) is diagnosed with acute promyelocytic leukemia (APL) at the age of 2, Sara and Brian Fitzgerald (Cameron Diaz and Jason Patric) are willing to do whatever it takes to save her life. And once her doctor explains that her best chance at beating the disease lies in finding a stem cell donor who’s an exact genetic match, they decide to have another child, knowing that they can achieve their goal via in vitro fertilization.
From birth, the test tube baby’s life becomes intertwined with that of her sickly sibling when tissue is taken from her umbilical cord. As time goes on, Anna (Abigail Breslin) is subjected to a series of increasingly-invasive procedures as she is stuck, poked and prodded for assorted extractions of platelets, blood and bone marrow.
By the time she’s 11, Little Miss Stem Cells is asked to donate one of her kidneys because by then both of her big sister’s are failing. However, the surgeon also states that after this operation she’ll have to be careful for the rest of the life, which means she will never be able to be a cheerleader or play soccer again.