A 2-year-old boy who developed a thrombosis of the superior sagittal sinus due to inherited protein S deficiency is reported from the Hospital de Cruces, Vizcaya, Spain. While recovering from pneumonia, the patient had symptoms of an acute disseminated intravascular coagulation disorder associated with sinus thrombosis, left hemiparesis, focal seizures, and thrombosis of the left femoral vein. The paresis resolved within two months. 
COMMENT. Homozygous protein S deficiency, an autosomal dominant trait with partial penetrance, usually presents with purpura fulminans in the newborn period. Heterozygous cases are responsible for recurrent peripheral thromboembolisms mainly in adults. Cerebral venous thrombosis is a rare complication of protein S deficiency, but should be considered in the etiology of acute hemiparesis in children.