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

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.

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.

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.

The possibility of PS K196E mutation should be considered if other causes of CVT are ruled out and if protein S activity is decreased.