When I first met my patient, three years earlier, a woman in her mid-70s from Western Pennsylvania, she had just been given a diagnosis of myelofibrosis.

This disease is classified as a myeloproliferative neoplasm, in which a genetic abnormality revs up the inner machinery of cells in the bone marrow (“myeloid” cells), causing them to divide at a rate that far exceeds what is normal. As the cells proliferate, they secrete a chemical that causes the bone marrow to fill with scar tissue (“fibrosis”).

The remaining normal myeloid cells evacuate to safer territory in the spleen, and the spleen swells, squashing the nearby stomach but making the abdomen look overly full. Consequently, the person with the disease becomes progressively malnourished from an inability to take in enough calories. My patient had lost 25 pounds in the preceding six months as a result, even as her waistline expanded and made her feel uncomfortable, even unwieldy from her new girth.

I had prescribed the one drug approved by the Food and Drug Administration for such conditions, and it worked well for her: Her spleen shrank back to a normal size, she gained back some weight, and she had resumed having a good quality of life.