acquired hemophilia a is a rare but potentially life - threating bleeding disorder that is caused by autoantibodies against factor viii . acquired hemophilia a is usually suspected in patients with an isolated prolongation of the activated partial thromboplastin time ( aptt ) . we herein present a case of acquired hemophilia a with a normal aptt , intramuscular hematoma and cerebral hemorrhage . a 73-year - old man with a history of hypertension , gastric cancer and abdominal aortic aneurysm visited our emergency department complaining of gait disturbance , pain and swelling in his right leg . his leg had become swollen five days ago and he was not able to walk smoothly . he had not experienced any trauma or fever and had not undergone an operation in the past month . on examination , his blood pressure was 162/81 mmhg , heart rate was 81 beats per minute and body temperature was 36.4. his right thigh demonstrated tender swelling , and the neurological findings revealed a shot - stepped gait without any paralysis or sensory disturbance . laboratory test results revealed a hemoglobin level of 10.4 g / dl ( normal , 13.2 - 17.2 g / dl ) , hematocrit of 30.4% ( normal , 40.4 - 51.1% ) , a von willebrand factor activity of 203% ( normal , 60 - 170% ) , elevated fibrinogen of 569 mg / dl ( normal , 200 - 400 mg / dl ) and elevated d - dimer level of 1.5 g / ml ( normal , 0.0 - 1.0 g / ml ) . his aptt level of 34.7 seconds ( normal , 26.9 - 38.1 seconds ) was normal , while the prothrombin time international normalized ratio , platelet count and liver function were also within the normal ranges . a computed tomography ( ct ) scan demonstrated intramuscular hematoma in his right thigh ( fig . 1 ) . the ct also demonstrated no recurrence of gastric cancer , and no new expansion and false lumen enhancement of the abdominal aorta . he had not experienced any previous bleeding episodes , even during two previous surgeries ( for gastric cancer and for an abdominal aortic aneurysm ) , and he also had no family history of bleeding . computed tomography scan showing an intramascular hematoma in the right thigh . four days later , head magnetic resonance imaging ( mri ) was performed for further evaluation of his gait disturbance . mri showed an intracranial hemorrhage , which was responsible for the gait disturbance ( fig . mixing studies showed no correction by incubating for 2 hours at 37 patient 's plasma with equal volumes of normal plasma . the results of other studies showed a factor viii antibody with a titer of 1 bethesda unit / ml ( normal , 0 bethesda units / ml ) and decreased factor viii activity of 22.2% ( normal , 50 - 150% ) . these results confirmed a diagnosis of acquired hemophilia a. treatment with 40 mg oral prednisone was initiated without any inhibitor bypassing agents , and no further bleeding episodes occurred . in response to the treatment , the aptt normalized , while the factor viii activity was over 100% , and the factor viii antibody t2-weighted fluid - attenuated inversion recovery ( flair ) mri showing a right thalamic hemorrhage . there is the possibility of a normal aptt in the initial evaluation in a patient with acquired hemophilia a , and acquired hemophilia a rarely causes life - threatening intracranial hemorrhage . regarding the first issue , the diagnostic hallmark of acquired hemophilia a is usually based on the detection of an isolated prolongation of the aptt . many algorithms for making a differential diagnosis of acquired hemophilia a start from the isolated prolongation of the aptt ( 1,2 ) . however , a report from a quantitative case - based survey of physicians across multiple specialties suggested that a prolonged aptt may be overlooked even in actively bleeding patients , especially when the aptt is only slightly prolonged ( 3 ) . acquired hemophilia a with a minimally prolonged aptt of 41.0 seconds has also been reported ( 4 ) . in our patient , the initial aptt was normal ( 34.7 seconds ) on admission , and a prolonged aptt was detected for the first time on the 4th day . we speculated that the reason for the normal aptt at the initial evaluation was due to a low disease level with a titer of 1 for bethesda units / ml . if we had not repeated the coagulation studies , we might not have diagnosed this potentially life - threating disorder . this case is the first reported case of acquired hemophilia a with a normal aptt at the initial evaluation . regarding the second clinical issue , most patients with acquired hemophilia a have hemorrhage in the skin , muscles or soft tissues ( 5 ) , while intracranial hemorrhage is rare ( 6 ) . however , if it occurs , it sometimes leads to death ( 7,8 ) . in our patient , we detected intracranial hemorrhage and made a diagnosis of acquired hemophilia a before any life - threating events occurred . a delay in establishing a diagnosis for acquired hemophilia a can result in severe bleeding and death , and we should therefore investigate the underlying diseases with spontaneous hemorrhage cases of unknown cause , especially in elderly patients . in conclusion , in patients with acquired hemophilia a , there is the possibility of demonstrating a normal aptt at the initial evaluation , and life - threatening intracranial hemorrhage rarely occurs in patients with acquired hemophilia a. if the initial aptt is normal , we should nevertheless repeat coagulation studies and examine other coagulation studies including a mixing study , factor viii level and inhibitor to investigate the underlying diseases in elderly patients with a spontaneous hemorrhage of unknown etiology . it is not uncommon to see bleeding symptoms in elderly patients in an emergency department . however , we are prone to attribute these events to anticoagulation therapy , antiplatelet therapy or hepatic disorders . our case suggested that we should conduct repeated coagulation studies , in order to make a differential diagnosis of bleeding and also carry out adequate consultations with a hematologist .
we herein present a case of acquired hemophilia a with a normal activated partial thromboplastin ( aptt ) , intramuscular hematoma and cerebral hemorrhage occurring in a 73-year - old man . 
 the patient visited our emergency department with gait disturbance , pain and swelling in his right leg . 
 computed tomography ( ct ) and magnetic resonance imaging ( mri ) revealed intramuscular hematoma and intracranial hemorrhage . 
 the results of initial coagulation studies were normal , but repeated coagulation studies revealed an isolated prolongation of the aptt . 
 additional laboratory tests confirmed the diagnosis of acquired hemophilia a. if the initial aptt is normal , we should therefore repeat the aptt and also perform other coagulation studies including a mixing study , factor viii level and inhibitor , to investigate the underlying diseases in elderly patients with spontaneous hemorrhaging of unknown etiology .