Usefulness of Cross-Mixing Test for Immune Thrombocytopenia in a Pediatric Patient with Coagulation Abnormalities

抄録

A previously healthy, 1-year-old Japanese boy presenting with subcutaneous purpura and mucosal bleeding was admitted to our hospital. Blood cell count revealed thrombocytopenia, prompting a diagnosis of immune thrombocytopenia (ITP) for further investigation. However, coagulation tests showed prolonged activated partial thromboplastin time (APTT), and a cross-mixing test indicated an inhibitor pattern consisting of lupus anticoagulant (LA). His platelet count improved five days after immunoglobulin administration, and prolonged APTT recovered to normal range within one month. No thrombocytopenia or coagulation abnormalities were observed thereafter. ITP is characterized by isolated immunological thrombocytopenia, which can be triggered by various situations. Almost all patients with ITP typically show normal blood coagulation. Herein, we present a case of pediatric ITP with prolonged APTT due to the presence of antiphospholipid antibodies with LA activity, which was suggested to be produced by immunological events, such as a measles-rubella vaccination and/or upper respiratory infection. A cross-mixing test is an effective laboratory method for the differential diagnosis of patients with prolonged APTT.