Factor X Vorarlberg, a New Variant of Hereditary Factor X Deficiency^X

The proposita, a 56 years old woman, has a mild bleeding tendency. Prothrombin time was 112 sec (control 17.0 sec), stypven time 13.7 sec (control 11.5 sec) and APTT 54 sec (control 40 sec). Factor I, II (funct.and imm.), V, VII, VIII, IX, XI, XII, AT III were normal. - Factor X activity was < 1% by extrinsic system assay (tissue thromboplastin), 12% by RVV assay and 32% by intrinsic system (APTT) assay. Similar results were obtained when factor X activity was determined using the synthetic substrate S 2222, Immunoassay (antibody neutralisation, heterologous antibody to factor X) demonstrated a decreased level (20%) of immunoreactive factor X. The patient plasma had no inhibitory activity. Factor X activity could be completely absorbed on barium sulfate and eluted with 5% sodium citrate. It was eluted at the same position from a Sephadex G-200 column as normal factor X, but nad a slower electrophoretic mobility when subjected to disc electrophoresis. Family studies (22 members studied) suggest an autosomal recessive inheritance, A second unrelated family with the same defect was subsequently detected in the same valley of Vorarlberg (Austria). - It is concluded that this hereditary coagulation disorder is Je to a grossly abnormal factor X-molecule.

 

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