Long-lasting severe anemia following treatment with natalizumab for relapsing–remitting multiple sclerosis: a case report

Abstract

Background Natalizumab is a monoclonal antibody used to treat patients with relapsing–remitting multiple sclerosis. Anemia is a recognized side effect, but it is usually mild and of a short duration when natalizumab is stopped. Here, we describe a case of a young woman with severe and especially long lasting anemia associated with treatment with natalizumab, persisting up to a year after treatment was stopped.

Case presentation A 24 year-old Caucasian woman with relapsing–remitting multiple sclerosis developed severe transfusion dependent anemia after 27 infusions with natalizumab, which was her first and only treatment for her multiple sclerosis. Extensive hematologic diagnostics did not reveal any malignant cause or any other plausible non-malignant cause for her anemia. The bone marrow was found to be hypercellular, with a maturation arrest of the erythropoiesis and with grade 1–2 fibrosis. No specific treatment for the anemia was given. The hemoglobin level showed signs of spontaneous increase after nearly one year after natalizumab was discontinued.

Conclusion Severe anemia can be caused by treatment with natalizumab. This case adds information to the few other similar reported cases, demonstrating the potential duration of the anemia, as well as detailed description of hematologic findings. The mechanism is most likely due to inhibition of α4 subunit of the α4β1-integrin, which is present on both lymphocytes and erythroid precursor cells.