Relationship between SF3B1 mutant allele burden and proportion of ring sideroblasts. Values for percentage of ring sideroblasts are grouped here in 3 arbitrary categories: < 15% (n = 183), 15% to 50% (n = 85), and > 50% (n = 57). Data are shown in a box plot depicting the smallest and largest observation (lowest and highest horizontal line, respectively), lower and upper quartile with median value (box), and outliers (dots).