Molecular relapse in the setting of imatinib dose de-escalation in FIP1L1/PDGFRA-positive CEL. Results of molecular testing for FIP1L1/PDGFRA by nested RT-PCR (rectangular bar beneath graph) are shown for 7 subjects as a function of time. The subject number is indicated by the white numeral. Each rectangle represents a 1-month period. Black rectangles indicate the presence of the fusion gene, and gray rectangles indicate the absence of the fusion gene. White rectangles represent months during which testing was not performed. Imatinib dose (y-axis) as a function of time (x-axis) is indicated by the gray shaded area. The dashed line in graph 1 represents the eosinophil count over time for this subject. All 5 subjects who underwent dose de-escalation (A), and neither subject who was maintained on stable high-dose imatinib (B), experienced molecular relapse.