Asymptomatic Homozygous nt 20210 G to A Prothrombin Polymorphism in Two Blood Donors Belonging to Two Different Kindreds

Abstract

The nucleotide (nt) 20210 G to A prothrombin polymorphism has been associated with an increased incidence of thrombosis, particularly venous thrombosis. The increased incidence of thrombosis resulted from an increase in prothrom bin levels. Two homozygous patients with this abnormality were found to be completely asymptomatic. In one of the two cases there was no thrombosis even after the additional risk factor of oral contraceptive therapy for several months. Pro thrombin activity and antigen as assayed by several methods were at the upper limits of normalcy in one case and slightly elevated in the other. The two cases described in this article do not rule out the possibility that this prothrombin abnormality be associated, given special acquired circumstances, with throm bosis. However, they indicate that extreme caution is needed to avoid an inaccurate conclusion. The fact that homozygous pa tients may remain asymptomatic indicates that the prothrom botic defect is very mild, if any. Key Words: Prothrombin— 20210 G to A abnormality—Thrombosis—Polymorphism.

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