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Intensive exposure to factor VIII is a risk factor for inhibitor development in mild hemophilia A
A Sharathkumar1, D Lillicrap, V S Blanchette
1Division of Haematology/Oncology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada M5G 1X8.
Background:
Inhibitors are rare in boys with mild hemophilia A (MHA; factor (F)VIII:C > 5%) but may arise following intense FVIII exposure, e.g. continuous infusion (CI).
Objectives:
To determine the impact of intense FVIII exposure in inhibitor formation in MHA at our institution and to compare this with previous reports.
Patients And Methods:
We reviewed FVIII exposure and inhibitor development in boys (ages 0-18 years) with MHA followed at our institution from 1996 to 2001 and conducted a Medline search (1966-2002) on the experience of inhibitor development following intensive/CI exposure to FVIII.
Results:
We identified 54 boys with MHA. Twenty-nine (54%) had been exposed to FVIII. Seven had received FVIII by CI. Four developed inhibitors; three high titer (at ages 10 years, 16 years and 17 years) and one low titer (at 1 month old). All four had received a CI of recombinant (r) FVIII of at least 6 days within 6 weeks of developing inhibitors. Baseline FVIII levels fell to < 1% in all cases and the three with high-titer inhibitors developed severe bleeding. Immune tolerance therapy (ITT) was attempted in two boys and was successful in one. Our literature search identified 35 cases (only four children) with MHA developing inhibitors following intense FVIII exposure often in the context of surgery.
Conclusions:
The incidence of inhibitors in our MHA population was 7.4%. If expressed according to exposure the incidence was significantly higher: 14% (4/29) for any exposure to FVIII and 57% (4/7) for exposure by CI. A prospective study to address whether CI is associated with an increased incidence of inhibitor development in MHA is warranted.
Insights
Intense factor VIII (FVIII) exposure, particularly continuous infusion (CI), significantly increases inhibitor development risk in boys with mild hemophilia A (MHA). Further research is needed to confirm this association.
Area of Science:
- Hematology
- Immunology
- Pediatrics
Background:
- Inhibitor development is uncommon in mild hemophilia A (MHA).
- Intense factor VIII (FVIII) exposure, such as continuous infusion (CI), may increase inhibitor risk in MHA patients.
- Understanding this risk is crucial for managing MHA.
Observation:
- A review of 54 MHA boys (ages 0-18) from 1996-2001 identified 29 exposed to FVIII.
- Seven patients received FVIII via CI, and four developed inhibitors (three high-titer, one low-titer).
- All four inhibitor cases received at least 6 days of recombinant FVIII CI within 6 weeks of inhibitor detection.
Findings:
- The overall incidence of inhibitors in the MHA cohort was 7.4%.
- Incidence rose to 14% with any FVIII exposure and 57% with CI exposure.
- High-titer inhibitors led to severe bleeding, necessitating immune tolerance therapy (ITT) in two patients.
Implications:
- Continuous infusion (CI) of factor VIII (FVIII) may be associated with a higher incidence of inhibitor development in mild hemophilia A (MHA).
- Prospective studies are warranted to definitively establish the link between CI and inhibitor formation.
- This finding has significant implications for treatment strategies and monitoring in MHA patients.