Acquired Hemophilia A with a Rare Presentation of Acute Subdural Hematoma

An 80-year-old man was admitted for acute subdural hematoma caused by a mild brain injury. His coagulation test showed an isolated prolongation of activated partial thromboplastin time (aPTT). Though the subdural hematoma did not progress, oozing bleed from the wound of tracheostomy continued. Failure of correction on aPTT mixing test supported the presence of an inhibitor to a coagulation factor. Once the diagnosis of acquired hemophilia A (AHA) was made, steroid therapy was performed, which leads him to complete remission of AHA. Isolated prolongation of aPTT can be the key to diagnose a rare coagulopathy, such as AHA.