6 Consecutive Patients and 100% of Inhibitors: is Inhibitor Development Inevitable?
ISTH Academy. Oliveira C. Jul 9, 2019; 264653; PB1463
Dr. Cristina Oliveira
Dr. Cristina Oliveira
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6 Consecutive Patients and 100% of Inhibitors: Is Inhibitor Development Inevitable?

C. Catarino1, E. Parcelas2, C. Jacinto Correia1, S. Campaniço1, F. Rodrigues1, A. Pereira1, E. Rocha3
1Centro Hospitalar Lisboa Norte - Hospital de Santa Maria, Imunohemotherapy, Lisboa, Portugal, 2Centro Hospitalar Lisboa Ocidental - Hospital de São Francisco Xavier, Immunohemotherapy, Lisboa, Portugal, 3Centro Hospitalar do Algarve - Hospital de Faro, Faro, Portugal

Main Topic: Hemophilia and Bleeding (including Transfusion)
Category: Hemophilia - Clinical

Background: Inhibitor development (ID) is the most significant treatment complication in patients with severe hemophilia A.
Aims: To evaluate the incidence of inhibitors and of factors related to ID in hemophilia A patients, diagnosed in our center, over a 2 year period.
Methods: Evaluation of clinical characteristics and potential risk factors for ID in 6 consecutive severe hemophilia A patients diagnosed between Sep2016-Sep2018.
Results: Six patients were diagnosed with severe hemophilia A in the above mentioned period. The average age of diagnosis was 8,43months (0-18) and the median age 4,4months. In all patients, the reason for diagnosis was a bleeding episode, of which three were severe hemorrhages (intracranial, paravertebral and postpartum cephalic hematoma). The age at first exposure to FVIII concentrate was 9,8months on average. Patients were treated with 4 different recombinant FVIII products. Primary prophylaxis was started in just 1 patient, weekly, at a low dose, at 12 months of age. The other patients started treatment due to bleeding, but intensive treatment was just performed in 2 of these patients. All patients developed high titer inhibitors (none with a family history), with a median of 21 Exposure Days (ED 6-31) and median age of detection of 13,1 months. Initial inhibitor titer ranged between 1,9 and 30 BU, and maximal titer between 14 and 143 BU. Only four patients have genetic results but in all 4 high risk mutations were identified. Immune tolerance induction was performed with success in 2 patients.
Conclusions: This high incidence of ID doesn't reflect the statistic reality, especially because of the small number of patients reported. Besides the high risk mutations, it is difficult to conclude about other risk factors for ID in these patients. We think his work only demonstrates the unpredictability of ID and how little we know about this serious complication of haemophilia treatment.

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