[Hereditary protein S deficiency and familial thrombosis. A review with description of a Danish family with protein S deficiency].

Protein S is approximately 69,000 Da polypeptide that acts as a co-factor in conjunction with activated protein C, in the natural anticoagulant system of protein C which irreversibly cleaves activated coagulation factors Va and VIIIa on the cell surface. Although synthesis of protein S takes place in several tissues, the hepatic production of protein S is presumably the most important. It has been established that heterozygous deficiency of protein S may be found in families with increased tendency to thrombosis (thrombophilia). The protein S gene, located on chromosome No. 3, consists of a translated gene, denoted PS alpha, and homologous untranslated region, designated PS beta. In inherited protein S deficiency deletions in PS alpha and PS beta have been detected. The present report deals with a Danish family with highly increased tendency to thrombosis, the propositus of which is a male who developed a large deep-vein thrombosis at the age of 18 months. In this family, nine cases with a plasma level of total protein S close to 50% of normal were identified, six of which had experienced one or more incidents of thrombosis in the past. We recommend that young patients who develop spontaneous arterial or venous thrombosis should be tested for the presence of inherited abnormalities of natural anticoagulants like antithrombin-III and proteins S and C.