title: Severe thrombocytopenia due to host-derived anti-HPA-1a after non-myeloablative allogeneic haematopoietic stem cell transplantation for multiple myeloma: a case report.
abstract: OBJECTIVE
  Host- or donor-derived alloimmune thrombocytopenia can develop after non-myeloablative allogeneic haematopoietic stem cell transplantation (HSCT). We report the first case of host-derived HPA-1a antibodies.
  
  
  METHODS
  A 52-year-old male patient received HSCT from his human leucocyte antigen (HLA)-A, -B, -C, -DR identical brother after reduced intensity conditioning. Bilinear engraftment around day 12 was accompanied by a continuous decrease of platelet counts. We investigated for platelet antibodies because of a progressive decline of platelet counts and refractoriness to platelet transfusions.
  
  
  METHODS
  The patient's serum was tested by enzyme-linked immunosorbent assay (ELISA), a solid phase assay and monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay. Recipient's DNA from the time before HSCT and donor's DNA were genotyped for human platelet antigens.
  
  
  RESULTS
  Serum obtained on day 15 after HSCT reacted strongly with the donor's platelets due to host-derived anti-HPA-1a- and anti-HLA I antibodies. Serum samples from days 39, 45 and 65 after HSCT contained only anti-HLA I; no antibodies were detectable on day 149. Platelet counts increased on day 20 spontaneously. The decrease of the antibodies accompanied by the increase of the platelet counts suggests progressive elimination of residual host cells.
  
  
  CONCLUSIONS
  The HPA-1a antibodies affected thrombopoietic engraftment and the success of platelet transfusions.
authors.affiliation: Department for Blood Group Serology and Transfusion Medicine, Medical University of Graz, Austria. susanne.macher@klinikum-graz.at
authors.forename: S
authors.initials: S
authors.lastname: Macher
authors.forename: K
authors.initials: K
authors.lastname: Schallmoser
authors.forename: P B
authors.initials: PB
authors.lastname: Staber
authors.forename: P
authors.initials: P
authors.lastname: Neumeister
authors.forename: U
authors.initials: U
authors.lastname: Posch
authors.forename: G
authors.initials: G
authors.lastname: Lanzer
authors.forename: S
authors.initials: S
authors.lastname: Panzer
mesh_terms: D016824:Antigens, Human Platelet / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology; D006085:Graft Survival / Q000276:immunology; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D039661:Integrin beta3; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000150:complications* / Q000276:immunology / Q000628:therapy; D017713:Platelet Transfusion; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000209:etiology* / Q000276:immunology; D014184:Transplantation, Homologous
chemical_list: D016824:Antigens, Human Platelet; D001323:Autoantibodies; C061248:ITGB3 protein, human; D039661:Integrin beta3