title: Gradual thrombocytopenia induced by long-term trastuzumab exposure.
abstract: OBJECTIVE
  Unexplained thrombocytopenia is a common clinical problem, and the possibility of drug-induced thrombocytopenia must be considered. Moreover, chemotherapy agents are known to typically cause thrombocytopenia by suppressing haematopoiesis, but they can also cause immune thrombocytopenia in which the mechanism involves antibody-mediated platelet destruction.
  
  
  METHODS
  We report a case of severe thrombocytopenia related to trastuzumab administration in which the patient exhibits a slow drift downward in platelet counts with repeated cycles of trastuzumab. A 70-year-old woman received a diagnosis of breast cancer and was treated with trastuzumab. She was confirmed to have a severe trastuzumab-induced thrombocytopenia after the 4th cycle. Retreatment with trastuzumab was not attempted.
  
  
  CONCLUSIONS
  Considering that trastuzumab is being increasingly used and that severe thrombocytopenia is a potentially life-threatening complication, its association must be seriously considered.
authors.affiliation: Department of Pharmacy, Mataro Hospital, Mataro, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Miarons
authors.affiliation: Department of Oncology, Mataro Hospital, Mataró, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Velasco
authors.affiliation: Department of Pharmacy, Mataro Hospital, Mataro, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Campins
authors.affiliation: Department of Oncology, Mataro Hospital, Mataró, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Fernández
authors.affiliation: Department of Hematology, Mataro Hospital, Mataró, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Gurrera
authors.affiliation: Department of Hematology, Mataro Hospital, Mataró, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Lopez-Viaplana
mesh_terms: D000368:Aged; D000970:Antineoplastic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy; D005260:Female; D006801:Humans; D010976:Platelet Count / Q000379:methods; D013921:Thrombocytopenia / Q000139:chemically induced*; D000068878:Trastuzumab / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D000970:Antineoplastic Agents; D000068878:Trastuzumab
keywords: adverse effect; adverse event; breast cancer; immune thrombocytopenia; monoclonal antibody; trastuzumab