Troubleshooting an isolate prolongation of activated partial thromboplastin time in a patient with acute myocardial infarction-a paradigmatic case report.

We describe here the case of a 46-year-old man admitted to the emergency department (ED) and diagnosed with a non-ST elevation myocardial infarction. Before referring the patient to the coronary care unit and initiating antiplatelet and anticoagulant therapy, a highly prolonged activated partial thromboplastin time (APTT) was observed among results of laboratory testing. Results of mixing test showed complete correction of APTT, thus ruling out the presence of inhibitors of blood coagulation. On the following day, second line coagulation testing revealed normal activity of all clotting factors except factor XII, the concentration of which was found to be 1.5%. This result was suggestive for a diagnosis of inherited factor XII deficiency, thus highlighting the importance of combining clinical history, symptoms and results of first-line coagulation tests in similar emergency conditions.