TREATMENT OF CONGENITAL THROMBOTIC SYNDROMES

Hereditary antithrombin III deficiency,protein C deficiency, and protein S deficiency predispose to the occurrence of venous thrombotic disease at a relatively youngage and often without an apparent cause. These disorders inherit as an autosomal dominant trait. Heterozygotes are at risk fosuperficial thrombophlebitis, thrombosis atnearly every venous site, and pulmonary embolism. Homozygous protein C deficiency may present itself with a purpura fulminans syndrome shortly after birth.In the acute phase of venous thromboembolism heparin is effective for preventing extension of the thrombotic process, and pulmonary embolism. In patients with antithrombin III deficiency the concomittant useof antithrombin III concentrate is controversial, although some patients may requirehigher doses of heparin.Substitution therapy is only indicated in homozygous protein C deficient patientswith purpura fulminans. Fresh frozen plasma i.v. is the treatment of choice, in a dosage of 10 ml/kg once or twice daily. The current prothrombin complex concentrates may induce new skin lesions and disseminated intravascular coagulation. After the lesions have been healed(mostly in 4 to6 weeks)coumarin therapy may effectively prevent new episodes of purpura fulminans, provided the prothrombin time is kept within 2,5 - 4,0 INR. Heparin is ineffective for preventing purpura fulminans due to homozygous protein C deficiency.The thrombotic manifestations in heterozygotes are effectively prevented by coumarin therapy. This is supported by the observation that patients may remain free of thrombosis during long-term treatment and may have recurrences shortly after the withdrawal of the coumarin drug. The therapeutic range for the prothrombin time should be within 2,0 - 4,0 INR, target value 3,0 INR. In the initial phase of oral anticoagulant therapy protein C deficient patients are prone to the development of coumarin induced hemorrhagic skin (tissue) necrosis.In the patients studied in Leiden, it occurred in about 3% of the treated patients. Heparin appears to be ineffective for the prevention of coumarin-induced skin necrosis; high loading doses of coumarin should be avoided and the prothrombin timeshouldbe checked dialy during the initial phase of oral anticoagulant treatment. Tissue necrosis may contribute to bleeding complications after fibrinolytic therapy, ashas been observed in two protein C deficient patients.In clinical situations with an increased risk for thrombosis such as surgery and pregnancy, heparin (in-low-doses) alone orin combination with coumarins have been used succesfully for the prevention of thrombosis. The need for antithrombin III concentrates in patients with hereditary antithrombin III deficiency in such situations is not substantiated.Although anabolic steroids are capable to increase the plasma concentrations of antithrombin III and of protein C in the respective deficiency states, its efficacy in preventing thrombotic episodes remains to be established.An optimal strategy for preventing thrombosis in congenital thrombotic syndromes is to identify still asymptomatic patients. In case of antithrombin III, protein C, and protein S deficiency this search is feasible. During risk situations for thrombosis patients are to be protected against the development of thrombosis.In Leiden pregnant women with one of the deficiencies are treated from the 14th week of pregnancy, initially with a shortacting coumarin drug, after the 34th week withheparin s.c. b.i.d. at therapeutic dosages,and after delivery coumarin therapy is reTnstituted during 6 weeks. The use of oralcontraceptives should be avoided, unlesspatients are under coumarin treatment. As long as deficient patients remain asymptomatic no antithrombotic treatment is indicated. After the first documented thromboticincident patients are treated indefinitelywith oral anticoagulants.