The Heterogeneity of Congenital factor X deficiency. A study of two unrelated patients

Two unrelated patients with congenital factor X deficiency are described. R.N. a four year old Pakistani child of consanguinous marriage presented with gastrointestinal haemorrhage. Routine tests of coagulation revealed a grossly prolonged prothrombin time and KCCT. All factor assays, other than factor X, were normal. Factor X, measured by three unrelated methods, was < 1%. Factor X related antigen (FXRAg) measured by antibody neutralisation was undetectable. In other, less affected members of the family FXC/FXRAg = 1 An infusion of factor X concentrate raised the factor X to 140%. The rate of decline was biphasic with an initial rapid component, T½ = 4 hours, and a slower second component T½ = 33 hours. The second patient, P.P. a Caucasian female presented with persistent post-dental extraction haemorrhage. Routine tests of coagulation revealed a prolonged prothrombin time and KCCT. All factor assays, other than factor X, were normal. Factor X, measured by two unrelated methods was 20 - 32% (normal 58- 134%) FXRAg was 71% (normal 60 - 120%). FXC/FXRAg = 0.35. Similar ratios were obtained on three other affected members of the family. The ratio represents an Important difference between the two families. Studies using the modified thrombotest strongly suggest an abnormal molecular complex in P.P. The results provide further evidence of the heterogenity of factor X deficiency states.