A family with hereditary factor X deficiency with a point mutation Gla(32)to Gln in the Gla domain (factor X Tokyo)

We report a new family with hereditary factor X deficiency. The propositus had a markedly prolonged prothrombin time, a mild prolongation of activated partial thromboplastin time and a clotting time activated by Russell's vip er venom, Factor X activity in plasma was 3 u/dl (normal range 56-138 u/dl) . Factor X antigen level was 61 u/dl, Molecular analysis revealed a homozyg ous mutation, Glu (GAG) to Gln (CAG) at residue 32 which normally undergoes gamma-carboxylation within the gamma-carboxyglutamic acid rich domain. The genotypes of family members completely correlated with their factor X acti vities. It is suggested that the Glu(32) to Gln mutation is the molecular b asis for the abnormal factor X in this family.