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Diagnosis of von Willebrand disease type 2N: A simplified method for measurement of factor VIII binding to von Willebrand factor
Author(s) -
Miller Connie H.,
Kelley Leslie,
Green David
Publication year - 1998
Publication title -
american journal of hematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.456
H-Index - 105
eISSN - 1096-8652
pISSN - 0361-8609
DOI - 10.1002/(sici)1096-8652(199808)58:4<311::aid-ajh11>3.0.co;2-a
Subject(s) - von willebrand disease , von willebrand factor , polyclonal antibodies , recombinant dna , medicine , antibody , coagulopathy , microbiology and biotechnology , immunology , chemistry , platelet , biochemistry , biology , gene
Diagnosis of von Willebrand disease Type 2N (vWD 2N), which mimics hemophilia A and its carrier state, is important for accurate genetic counseling and appropriate therapy. To make testing for the disorder more clinically applicable, we developed a simplified method for measurement of factor VIII (FVIII) binding to von Willebrand factor (vWF) using commercially available reagents and standard clinical assays. FVIII binding to vWF was measured by capture of patient vWF by polyclonal antibodies on cyanogen bromide‐activated Sepharose beads, reaction with recombinant FVIII, and assay of unbound FVIII by clotting methods. Unbound vWF was measured in patient plasma after capture by the Laurell method. The ratio of bound FVIII/bound vWF was normal in hemophilia A, vWD Type 1, and vWD Type 3 patients, and abnormal in 5 subjects from two families, all of whom had vWD 2N mutations. Patient 1, with FVIII 8 U/dl, vWF: Ag 61 U/dl, vWF:RC 74 U/dl, and FVIII binding nil, was homozygous for the Arg91Gln mutation. She was followed during pregnancy and delivered an unaffected heterozygous son. Patient 2 had FVIII 8 U/dl, vWF:Ag 73 U/dl, and vWF:RC 71 U/dl, and very low FVIII binding. She was heterozygous for Arg91Gln, as were her mother and sister; no second vWD 2N mutation was found. Her brother, with FVIII 14 U/dl, vWF:Ag 113 U/dl, and vWF:RC 72 U/dl, has no evidence of vWD 2N. With an X‐linked inheritance pattern of bleeding tendency, this family is the first reported with combined hemophilia A and vWD 2N. Am. J. Hematol. 58:311–318, 1998. © 1998 Wiley‐Liss, Inc.