Thrombocytopenia is a major cause of morbidity and hospital expense following
bone marrow transplantation.
Platelet transfusions in these patients are frequently complicated by the recipient's development of
antibodies to HLA
class I antigens. When these patients become refractory to the transfusion of HLA-matched platelets, the recipient's platelet
antigen phenotype must be determined, to ensure that donor platelets will be phenotypically compatible. Cases of alloimmunization to
HPA-1a and HPA-1b resulting in refractoriness to transfused platelets and the subsequent development of a
posttransfusion purpura-like syndrome are reported.
CASE REPORTS: In the first case, a 43-year-old woman with Stage IV infiltrating ductal
breast cancer presented to the hospital for a transplant of autologous peripheral blood stem cells. After the transplant, her platelet count remained less than 10 x 10(9) per L, despite daily
platelet transfusions, including HLA-matched platelets. Fourteen days following the transplant, her serum was found to contain anti-HPA-1a. Initially, the patient was refractory to the transfusion of HPA-1a-negative platelets, but
after treatment with
intravenous immunoglobulin, she had transient increases in posttransfusion platelet counts. She was also treated with a
staphylococcal protein A immunoadsorption column and has not had any such subsequent refractoriness. Her genotype has been found, by use of allele-specific
oligonucleotide hybridization with white cell
DNA, to be HPA-1b/1b. The second case involved a 32-year-old woman with
chronic myelogenous leukemia who received an unrelated-donor marrow transplant. Three years later, her CML recurred, and she was treated with
interferon-alpha. Four months afterward, she experienced
interferon-alpha-induced
thrombocytopenia and the
interferon therapy was discontinued. She received 12
platelet transfusions in 20 days, but none was effective.
Antibodies specific for
HLA antigens and HPA-1b were detected, and three HLA-matched, HPA-1b-negative
apheresis platelet components were given, but without effect. Two days
after treatment with
methylprednisolone (1 g intravenously) and
prednisone (2 mg/kg/day orally), her platelet count was 26 x 10(9) per L, and after 8 more days, it was 102 x 10(9) per L, without further transfusions. She was found to be homozygous for
HPA-1a (HPA-1a/1a).
CONCLUSION: Anti-HPA-1a and anti-HPA-1b can cause refractoriness to
platelet transfusions in bone marrow transplant patients. Testing for platelet-specific
antibodies should be considered in all patients who are refractory to HLA-matched platelets.