Heterozygous plasminogen deficiency was found in 2 patients (mother and daughter). The mother, aged 55 years, was symptomatic while the daughter, aged 10 years, was asymptomatic so far. The thrombotic tendency presented by the proposita (mother) was severe and included recurrent superficial, portal, mesenteric, subclavian thrombophlebitis. No arterial thrombosis was noted. Oral anticoagulants have been of some benefit. The main laboratory features were: plasminogen activity about 50% of normal in two amidolytic methods and in a caseinolytic method. Plasminogen antigen was also about 50% of normal using electroimmunoassay and radial immunodiffusion. Crossed immunoelectrophoresis revealed a normal, even though reduced pattern, thus excluding dysplasminogenemia. Routine coagulation tests were negative. Euglobulin lysis time, fibrinogen level and fibrinogen degradation products (FDP) were within normal limits. Antithrombin III, protein C and protein S were also within normal limits.

In a family with a known antithrombin III abnormality (AT III Trento) an associated von Willebrand defect (Type I) was found. The two defects seem to segregate independently. In fact four types of individuals were present, namely: subjects with isolated AT III abnormality, subjects with isolated von Willebrand defect, patients with double defect and normal subjects. Only one of the two patients with isolated AT III abnormality showed a thrombotic tendency. None of the patients with double defect showed thrombotic disease, indicating a possible protective action of the von Willebrand defect against thrombotic manifestations. Patients with isolated von Willebrand defect showed neither thrombotic nor bleeding manifestations. The study emphasizes the need for a careful evaluation of the hemostatic balance of patients with AT III abnormalities before concluding that they are symptomatic or asymptomatic.

A family with a new congenital abnormality of antithrombin III (AT III) is presented. 5 members, all females, were affected. The proposita has had several thrombotic manifestations. The other patients, so far, are asymptomatic. Antithrombin activities were all decreased regardless of the method used (chromogenic or clotting) and regardless of the presence or absence of heparin in the assay system. AT III antigen, on the contrary, was normal in all patients regardless of the method used (electroimmunoassay, radial immunodiffusion or Laser nephelometer). The crossed immunoelectrophoresis without heparin showed in plasma the presence of an abnormal peak which was more anodal than the normal counterpart. The same pattern was seen in serum. In the heparin-modified cross-immunoelectrophoresis a normal pattern was seen in plasma and an abnormal one in serum. In the latter the anodal peak was in fact larger than the normal counterpart. Chromatographic studies using Heparin-Sepharose column failed to show changes in heparin affinity, and indicated that both the normal and the abnormal peak were contained in the major AT III area. The toponym AT III Trento is proposed to describe this abnormality. These studies further emphasize the great heterogeneity of AT III defects. This is the first AT III abnormality to show an abnormal crossed-immunoelectrophoresis in the absence of heparin.