This article contained a very disturbing comment: “Neurologist Annette Langer-Gould of Stanford University says that even the 1-in-1,000 risk of PML [leukemia] ‘seems to outweigh the benefits’ that natalizumab would provide many patients.” Having a genetic mutation for which there is no treatment or cure and having (and having had) friends with MS, I am very concerned that some entity would withhold a beneficial treatment because of an identified risk.