acquired hemophilia a ( aha ) , a rare bleeding disorder triggered by autoantibodies against factor viii ( fviii ) , occurs without a family history of hemophilia.1 bleeding is usually mucocutaneous , soft tissue , or gastrointestinal , and is often severe or even life threatening .
there is a reported mortality rate of 9.7%33%.2 aha invariably causes a prolonged activated partial thromboplastin time ( aptt ) , and the laboratory diagnosis is confirmed by demonstrating a reduced fviii level along with a detectable fviii inhibitor.1 up to 85% of affected individuals are older adults ( > 60 years ) of either sex.1 to date , the underlying causes of aha are still under debate . in more than 50% of aha cases ,
the remaining cases may be associated with autoimmune diseases , the postpartum period , infections , vaccinations , underlying hematologic diseases , or solid cancer.3 moreover , an analysis of literature data showed several cases of drug - induced anti - fviii autoantibodies , highlighting this finding as one of the most relevant causes of aha.4 recently , some cases of aha associated with antiplatelet drug such as clopidogrel5,6 and vitamin k antagonist , like warfarin,710 have been reported .
this makes the diagnosis of drug - associated autoantibodies against fviii a complicated challenge , since the sudden onset of bleeding might be erroneously attributed to these drugs .
clopidogrel , prasugrel , or ticagrelor , plus aspirin , is the most commonly used treatment for patients with acute coronary syndrome : the so - called dual antiplatelet therapy ( dapt).11 ticagrelor is an orally administered direct - acting p2y12 receptor antagonist that is not a prodrug and does not require metabolic activation for antiplatelet activity , unlike clopidogrel and prasugrel , that binds irreversibly to the receptor for the life of the platelet.11 pharmacodynamic studies have demonstrated that ticagrelor has a faster onset and inhibits platelet aggregation more strongly than does clopidogrel .
these properties may well contribute to reduced rates of thrombotic outcomes compared to clopidogrel , as demonstrated in a phase iii clinical trial ( plato trial).12 ticagrelor represents an advancement in p2y12 receptor inhibition therapy , and no distinctive adverse effects , other than bleeding , have been reported for this new chemical entity .
this report describes a patient , who has given consent for publication of all information about his clinical case , with aha associated with ticagrelor therapy who showed complete remission after steroid and cyclophosphamide administration , in spite of dapt continuation .
a 52-year - old man , treated with acetylsalicylic acid ( asa ) 100 mg / day and ticagrelor 180 mg / day ( dapt ) for recent percutaneous transluminal coronary angioplasty with medicated coronary stents , arrived complaining of right leg pain due to a relevant hemorrhagic effusion .
our patient had severe anemia ( hb 6.9 g / dl ) , prolonged aptt of 80 seconds , and normal prothrombin time and platelet levels .
the mixing test showed no normalization of the prolonged aptt after incubation with severe evident fviii deficiency ( 1.1% ) , due to a detectable fviii inhibitor ( 6.72 bethesda units [ bu ] ) confirming the diagnosis of aha .
extensive radiological / hematological examinations , ie , computed tomography of the chest and abdomen with contrast medium , laboratory testing for antinuclear antibodies , anti - dna antibodies , antiphospholipid antibodies , autoantibodies to extractable nuclear antigens , antineutrophil cytoplasmic antibodies , c- and s - reactive proteins , activated protein c resistance , and serum immunoglobulin tests were uneventful for any underlying disorders , such as connective tissue disorders , lymphoproliferative disease , or inflammatory bowel diseases .
on the basis of the aha diagnosis and in line with the standard guidelines for its management , prednisone at 100 mg and cyclophosphamide at 90 mg were administered daily . in the present case , skin , muscle , and soft tissue bleeding , and aptt prolongation developed within one month after ticagrelor had been added to the asa treatment , while aptt had been repeatedly normal before taking this drug .
the diagnosis was made one month later when the patient arrived to our attention after we had dosed an fviii inhibitor titer of 6.72 bu / ml . because of the high risk of stent thrombosis , ticagrelor and asa therapy was continued and treatment with prednisone at 100 mg and cyclophosphamide at 90 mg / day was promptly started .
following stabilization of the bleeding , the immunosuppressive therapy was continued until such time as there was eradication of the inhibitor .
after 10 days , aptt dropped from 107 to 49 seconds , the patient s fviii levels gradually normalized over the following few weeks , and the inhibitor titer was negative . therefore , the dosage of cyclophosphamide and prednisone was gradually reduced according to the inhibitor titer and the fviii level , but the ticagrelor therapy was not stopped .
he was given dapt antiplatelet therapy for one year as prescribed by his cardiologist because of the high risk of stent thrombosis , even though ticagrelor had most probably induced the disease .
according to the european acquired haemophilia registry ( each2 ) , aha may be idiopathic even if an underlying disorder is identified in about 50% of the patients.13 although the drug - induced anti - fviii antibodies have been reported to account for only 3%4 of aha , the real incidence could be underestimated .
moreover , drugs such as clopidogrel or warfarin might well mask the correct diagnosis of aha.510 therefore , some authors suggest that for elderly patients on clopidogrel or warfarin therapy presenting with unusual / unexplained bleeding , not only the treatment but also the possibility of aha should be carefully investigated.7 ticagrelor , the first reversible oral p2y12 receptor antagonist , provides faster , greater , and more consistent adenosine diphosphate receptor inhibition , thus becoming an accepted option in several clinical situations , such as unstable angina , non - st - segment elevation acute coronary syndrome , and percutaneous coronary intervention.11,14,15 in this case , we report a patient diagnosed as having developed ticagrelor - associated aha .
even though , to the best of our knowledge , no other such cases have been reported , our hypothesis is supported by several factors .
one important point is that the patient developed a severe bleeding disorder associated with a significant blood titer of an inhibitor against fviii one month after ticagrelor had been added to asa therapy and after repeatedly dosing a normal aptt .
the temporal relationship of the administration of the drug and the onset of the illness , the prompt clinical and laboratory response to corticosteroids , and the exclusion of causes other than drugs or confounding factors are in agreement with our hypothesis .
ticagrelor therapy was not suspended nor was it changed for other similar drugs such as clopidogrel .
first , the patient s critical clinical situation made it unadvisable to change the dosage or interrupt the drug .
third , clopidogrel may also induce aha.5,6 the naranjo algorithm16 was used to evaluate the likelihood of adverse drug reaction .
this questionnaire included 10 questions that rate adverse drug reactions using a numeric score that ranged from 4 to + 13 .
the reaction is considered definite if the score is 9 or higher , probable if it is from 5 to 8 , possible if it is from 1 to 4 , and doubtful if it is 0 or less .
there are previous similar conclusive reports on this reaction,5,6 the adverse event appeared after the suspected drug had been administered , and there were no alternative causes ( other than the drug ) that could have been responsible for the reaction .
moreover , the fact that several publications have reported that aha is an adverse event due to drug treatment is noteworthy , and recently , some reports have established a link between the development of aha and clopidogrel.5,6 this finding is in line with our hypothesis , since both ticagrelor and clopidogrel inhibit the p2y12 receptors even though ticagrelor shows properties that distinguish it from clopidogrel.11,14
this case report indicates that ticagrelor might trigger aha , even if an idiopathic form can not be excluded .
although ticagrelor and clopidogrel differ from a chemical point of view , they do share the same p2y12 receptor action and have the same adverse effect.5,6 a prompt response to prednisone and cyclophosphamide therapy was obtained in our patient , without suspending dapt therapy .
 we present a case report of a 52-year - old man who was hospitalized for right leg pain due to a relevant hemorrhagic effusion . 
 he was on dual antiplatelet therapy ( dapt ) : acetylsalicylic acid and ticagrelor , a reversible p2y12 receptor antagonist . 
 signs , symptoms , and laboratory blood tests led to the diagnosis of acquired hemophilia a ( aha ) . 
 ticagrelor therapy - associated aha was hypothesized due to the fact that , before adding this drug , all laboratory and clinical examinations were repeatedly normal . 
 prednisone and cyclophosphamide treatment was started without dapt interruption due to the high risk of stent thrombosis . 
 after 10 days , prolonged activated partial thromboplastin time dropped from 107 to 49 seconds , the patient s factor viii ( fviii ) levels gradually normalized over the following few weeks , and fviii inhibitor titer was negative . 
 recently , some reports have established a link between the development of aha and treatment with clopidogrel , an irreversible p2y12 receptor antagonist . however , to the best of our knowledge , this is the first time that a link between aha and ticagrelor has been reported . 
Introduction
Case Report
Discussion
Conclusions