AT III Barcelona: a familial quantitative-qualitative AT III deficiency

A quantitative and qualitative deficiency of antithrombin III (ATIII) was found in four members of a Spanish family with thrombotic tendency. In all affected members, levels of ATIII antigen and activity (heparin cofactor activity) were reduced to 50% of the normal range. When crossed immunoelectrophoresis (CIE) was performed in the presence of heparin, an abnormal slow-moving peak was found. Crossed immunoelectrofocusing (CIEF) from normal and affected individuals showed that normal ATIII migrated between pH 4.9-5.3 while the ATIII under study was asymmetrically distributed between two pH ranges: 4.9-5.3 and 4.6-4.8. Affinity adsorption of affected members' plasma to heparin-sepharose beads revealed one population of ATIII in the supernatant corresponding to the abnormal ATIII, devoid of heparin cofactor activity and showing a peak between pH range: 4.6-4.8 in CIEF. Our data supports the view that a quantitative-qualitative deficiency was present in the heterozygous state in all the affected family members. Both normal and abnormal ATIII were present in plasma of the affected individuals. This abnormal ATIII was characterized by a lack of affinity for heparin. This familial ATIII deficiency was named ATIII Barcelona.