Early Identification of Protein S K196E Mutation in a Patient With Cerebral Venous Thrombosis: A Case Report.

BACKGROUND: Mutation of protein S K196E (PS K196E) is a genetic risk factor for venous thromboembolism; however, there are few reports on cerebral venous thrombosis (CVT) with this mutation. We report a case of CVT that was diagnosed as having PS K196E mutation at the initial thrombotic event. METHODS: A 54-year-old man suddenly developed generalized seizures after headache and nausea. Brain magnetic resonance imaging showed cerebral edema, and angiography revealed CVT. Blood examination revealed that protein S activity was low (44%) despite normal free protein S antigen levels (81%). Sequence analysis revealed a heterozygous PS K196E mutation. We treated him with warfarin with the international normalized ratio maintained at 2.0-3.0. After 1 month, he was discharged without any neurological sequelae. RESULTS: Early identification of the causes of thrombophilia is important for the long-term management of CVT. However, detection of PS K196E mutation is difficult because its only feature is a moderate decrease in the activity of protein S, which is influenced by environmental factors. CONCLUSIONS: The possibility of PS K196E mutation should be considered if other causes of CVT are ruled out and if protein S activity is decreased.