title: Rapid acquisition of immunologic tolerance to factor VIII and disappearance of anti-factor VIII IgG4 after prophylactic therapy in a hemophilia A patient with high-titer factor VIII inhibitor.
abstract: We report an 11-month-old boy with severe hemophilia A who had regular exposure to factor VIII (FVIII) intended to reduce the risk of developing an inhibitor. He developed a high-titer inhibitor (peak titer 19 BU) that disappeared within 6 weeks of starting immune tolerance induction (ITI). Anti-FVIII IgG4 peaked briefly compared with anti-FVIII IgG1 and the Bethesda titer. Neither rapid resolution of an inhibitor after prophylaxis nor this behavior of anti-FVIII IgG4 has been previously reported. Transient anti-FVIII IgG4 may be a marker of an attenuated anti-FVIII response induced by prophylactic FVIII therapy.
authors.affiliation: *Janeway Children's Health and Rehabilitation Centre, St. John's, NF †Kingston General Hospital ‡Faculty of Health Sciences, Queen's University, Kingston, ON, Canada.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Moorehead
authors.forename: Lisa
authors.initials: L
authors.lastname: Thibeault
authors.forename: Angie
authors.initials: A
authors.lastname: Tuttle
authors.forename: Julie
authors.initials: J
authors.lastname: Grabell
authors.forename: Louise
authors.initials: L
authors.lastname: Dwyre
authors.forename: Mariana
authors.initials: M
authors.lastname: Silva
authors.forename: Paula
authors.initials: P
authors.lastname: James
authors.forename: David
authors.initials: D
authors.lastname: Lillicrap
mesh_terms: D005169:Factor VIII / Q000037:antagonists & inhibitors / Q000276:immunology*; D006467:Hemophilia A / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance; D007074:Immunoglobulin G / Q000097:blood*
chemical_list: D007074:Immunoglobulin G; D005169:Factor VIII