[A case of pseudothrombocytopenia due to platelet cold agglutinins].

We report a case of pseudothrombocytopenia due to platelet cold agglutinins. Platelet counts were decreased in blood drawn in a tube without anti-coagulant just after withdrawal as well as in blood drawn in a tube with anti-coagulant, such as EDTA-2K, MgSO4, citrate or heparin. In our case, platelet aggregates were noted on blood-smear made from blood samples obtained with and without anti-coagulant. RBC and WBC counts were within the normal range. Platelet aggregates mainly consisted of 2-5 platelets. Patient plasma agglutinated normal platelets at a temperature below 10 degrees C. Immunoglobulin class was determined as IgM by flow cytometry.