title: Hematologic modifications in natalizumab-treated multiple sclerosis patients: An 18-month longitudinal study.
abstract: OBJECTIVE
  To monitor the hematologic modifications in the peripheral blood of patients with relapsing-remitting multiple sclerosis treated with natalizumab.
  
  
  METHODS
  The cohort included 44 patients with relapsing-remitting multiple sclerosis treated monthly with natalizumab for 18 months. Peripheral blood was collected before treatment initiation and on a monthly basis during the treatment course. Complete blood cell count was performed using automated hematology systems. Blood smears were prepared and analyzed when abnormal values were detected.
  
  
  RESULTS
  Mean total white blood cell, lymphocyte, and eosinophil counts were significantly higher 1 month after treatment initiation and remained stable during the 18 months of follow-up. Monocyte counts increased progressively during the 18-month treatment with natalizumab. Erythroblasts and neutrophil precursors were absent before treatment initiation but were present in 16% and 6.8% of patients, respectively, 1 month after the first natalizumab infusion. The proportion of patients with erythroblasts and neutrophil precursors remained stable throughout the 18-month follow-up period. On an individual patient basis, a fluctuating level of erythroblasts and neutrophil precursors was observed. No difference in mean erythrocyte, hemoglobin, hematocrit, thrombocyte, and neutrophil levels was observed before and after 18 months of natalizumab treatment. No cases of myelodysplastic syndrome or acute leukemia were observed.
  
  
  CONCLUSIONS
  Chronic treatment with natalizumab is associated with significant modifications in complete blood cell count, including emergence of hematopoietic precursors that are not present in peripheral blood under normal conditions. None of these modifications were associated with malignancy.
authors.affiliation: Department of Clinical Neurosciences (C.B., P.H.L.), Division of Neurology, Unit of Neuroimmunology and Multiple Sclerosis; Department of Hematology (Y.B., K.S.); and Department of Genetics and Laboratory Medicine (P.H.L.), Laboratory Medicine Service, University Hospital of Geneva, Switzerland.
authors.forename: Claire
authors.initials: C
authors.lastname: Bridel
authors.affiliation: Department of Clinical Neurosciences (C.B., P.H.L.), Division of Neurology, Unit of Neuroimmunology and Multiple Sclerosis; Department of Hematology (Y.B., K.S.); and Department of Genetics and Laboratory Medicine (P.H.L.), Laboratory Medicine Service, University Hospital of Geneva, Switzerland.
authors.forename: Yan
authors.initials: Y
authors.lastname: Beauverd
authors.affiliation: Department of Clinical Neurosciences (C.B., P.H.L.), Division of Neurology, Unit of Neuroimmunology and Multiple Sclerosis; Department of Hematology (Y.B., K.S.); and Department of Genetics and Laboratory Medicine (P.H.L.), Laboratory Medicine Service, University Hospital of Geneva, Switzerland.
authors.forename: Kaveh
authors.initials: K
authors.lastname: Samii
authors.affiliation: Department of Clinical Neurosciences (C.B., P.H.L.), Division of Neurology, Unit of Neuroimmunology and Multiple Sclerosis; Department of Hematology (Y.B., K.S.); and Department of Genetics and Laboratory Medicine (P.H.L.), Laboratory Medicine Service, University Hospital of Geneva, Switzerland.
authors.forename: Patrice H
authors.initials: PH
authors.lastname: Lalive