Abstract
Lupus anticoagulant-hypothrombinemia syndrome (LAHPS) is characterized by positivity for the lupus anticoagulant (LA) accompanying hypoprothrombinemia and bleeding symptoms. Here, we report a case of LAHPS diagnosed by the activated partial thromboplastin time (APTT) mixing test. A 2-year-old girl presented with subcutaneous hemorrhage after developing tonsillitis. Since the prolongation of prothrombin time (PT) and APTT was pointed out in the coagulation tests, she was referred to our hospital. The APTT mixing test was carried out to investigate the cause of the prolongation of PT and APTT. As a result, the immediate-type and delayed-type waveforms exhibited similar convex upward patterns, which suggested the presence of LA. Additional tests confirmed the positivity for LA and low factor II activity (4.1%). Because she was negative for antinuclear antibodies, she was considered unlikely to have an autoimmune disease. On the basis of these results and her history of tonsillitis, the patient was diagnosed as having LAHPS that developed concomitantly with an infection. Therefore, we again realized that the APTT mixing test was useful for rapidly differentiating the causes of clotting time prolongation.
