These defects are responsible for only a moderate increase of venous thromboembolism (VTE) risk compared with strong thrombophilias (antithrombin III, protein C and protein S deficiencies and homozygous forms of factor V Leiden and G20210A prothrombin mutation).
It is an autosomal dominant disorder and is ten times more common in these patients than antithrombin III-, protein C- and protein S deficiency together.
Patients with AT III deficiency had an higher incidence of thrombosis than patients with Protein C or Protein S deficiency (12 vs. 2.8 vs. 3.3% pts.-ys, p < 0.05), despite the fact that they were, on average, younger and more prophylaxed.
Acquired antithrombin III deficiency: replacement with antithrombin III concentrates in a patient with protein S deficiency accelerates response to therapy.
In 107 asymptomatic and untreated patients with inherited syndromes associated with thrombophilia (antithrombin III, protein C and protein S deficiencies), we compared in parallel two plasma peptides which reflect activation of the common coagulation pathway: the prothrombin fragment 1 + 2 (F1 + 2) and fibrinopeptide A (FPA).
ATIII deficiency is found in between 4 and 6 percent of young patients with venous thrombosis, similar to but slightly lower than the prevalence of protein C and protein S deficiency in young subjects with thrombosis.
The frequency of heterozygous protein C and protein S deficiency, detected by measuring total plasma antigen, in a group (n = 141) of young unrelated patients (less than 45 years old) with venous thrombotic disease was studied and compared to that of antithrombin III, fibrinogen, and plasminogen deficiencies.