Bone marrow reticulin increased in one romiplostim-treated patient in the prospective study. Photomicrograph (original magnification ×20) of patient 11 before (Baseline) and after 3.2 months of romiplostim treatment (On treatment). The on-treatment bone marrow sample exhibited an increased number of megakaryocytes (arrowheads) and reticulin (grade 1-2; arrows) but no increase in cellularity.