Factor X Roma: a congenital factor X variant defective at different degrees in the intrinsic and the extrinsic activation.
A factor X molecular variant was identified in a 13-year-old girl affected by a bleeding tendency. Factor X antigen levels and activation by Russel's viper venom (tested both by clotting and amidolytic assays) were normal. Factor X crossed immunoelectrophoresis was found to be identical to that of the control plasma. Factor X functional activity was low (3% of the normal) if tested by PTT-derived assays, whereas it was found at intermediate levels (about 30-50% of the normal) if measured by prothrombin time-derived assays. The defect in the extrinsic activation was more clearly disclosed using as activating agent thromboplastin from ox brain. The factor X of the patient was completely adsorbed by aluminum hydroxide. The parents of the propositus (first degree cousins) showed factor X functional levels compatible with a condition of heterozygosity for the abnormality. This factor X molecular variant appears different from the other ones so far described and was named 'Factor X Roma'.
De Stefano
V
V
Istituto di Semeiotica Medica, Università Cattolica S. Cuore, Roma, Italy.
Leone
G
G
Ferrelli
R
R
Hassan
H J
HJ
Macioce
G
G
Bizzi
B
B
D000293:Adolescent; D000941:Antigens / Q000032:analysis; D005170:Factor X / Q000276:immunology / Q000378:metabolism; D005171:Factor X Deficiency / Q000503:physiopathology*; D005260:Female; D006474:Hemorrhagic Disorders / Q000097:blood; D006801:Humans; D007020:Hypoprothrombinemias / Q000503:physiopathology*
D000941:Antigens; D005170:Factor X