Improvement in bone marrow reticulin after cessation of romiplostim treatment. Photomicrographs (original magnification ×20) of bone marrow biopsies from patient 4 before romiplostim treatment (Baseline), during treatment (Week 26), and after discontinuation of treatment (Week 34 and Week 46). Sections stained with hematoxylin and eosin, reticulin, and trichrome stains as indicated. Megakaryocytes (arrowheads) were increased at baseline, markedly increased by week 26, and returned to baseline number by weeks 34 and 46. Reticulin (arrows) increased from grade 0 at baseline to grade 2/3 by week 26 followed by a decrease to grade 1 by week 46. Collagen fibrosis (trichrome stain) was not detected at any time. Blasts were not increased at any time.