title: Two allotypes of factor IX present in haemophilia B.
abstract: Factor IX antigen (IX:Ag) was measured with three different immunoradiometric assays (IRMAs) in 30 healthy people and 43 patients with haemophilia B of varying severity. Two of the IRMAs were based on monoclonal antibodies capable of differentiating between two genetically determined molecular variants of normal factor IX. Most patients with severe hemophilia B lacked demonstrable IX:Ag. The factor IX variant that is undetectable with one of the monoclonal antibodies used was present in 2 out of 6 families with moderate haemophilia B and in 1 out of 6 families with mild haemophilia B. The existence of allotypes of factor IX in hemophilia B may have practical implications for carrier detection and prenatal diagnosis.
mesh_terms: D000483:Alleles; D005164:Factor IX / Q000032:analysis*; D014644:Genetic Variation; D002836:Hemophilia B / Q000097:blood* / Q000235:genetics / Q000503:physiopathology; D006801:Humans; D009994:Osmolar Concentration; D011863:Radioimmunoassay
chemical_list: D005164:Factor IX