Diagnosis of Trousseau Syndrome Due to Lung Adenocarcinoma in a 77-Year-Old Man who Presented with Blue Toe Syndrome and a High CA125 Level: A Case Report

The patient was a 77-year-old man who initially presented with blue toe syndrome (BTS) and multiple cerebral emboli. He was diagnosed as having Trousseau syndrome due to lung adenocarcinoma. BTS is a rare presenting symptom in Trousseau syndrome, which is caused by blood hypercoagulability and is mainly associated with mucin-producing adenocarcinoma. Serum CA125 levels, a mucin production marker, increased together with plasma D-dimer level because of lung adenocarcinoma, which is rare. Anticoagulant therapy with heparin temporarily improved the D-dimer level and skin discoloration of BTS. Therefore, we believe that the BTS in this case was consistent with Trousseau syndrome.