[Changes in bone marrow MRI patterns in aplastic anemia before and after successful treatment with ATG].

In order to evaluate the usefulness of MRI in estimating bone marrow cellularity, we performed MRI of the lumbar spine in two patients with severe aplastic anemia, before and after successful treatment with antithymocyte globulin (ATG). Case 1, a 25-year-old man with idiopathic aplastic anemia, was treated with ATG 6 months after the onset. One month after treatment, his peripheral blood count and bone marrow cellularity recovered, and the MRI bone marrow pattern became normal. Case 2, a 78-year-old woman with drug-induced aplastic anemia, was treated with ATG 4 months after the onset. Three months after treatment, her peripheral blood count improved. Five months after treatment, her bone marrow cellularity recovered and the MRI bone marrow pattern was normal for her age. Seven months after treatment, when her peripheral blood count was almost normal, we observed hypercellular bone marrow restoration at the periphery of the vertebrae. MRI seems to be an effective method of evaluating bone marrow recovery in aplastic anemia.