MTHFR and hyperinsulinemic hypoglycemia, familial, 4: The most common types of primary thrombophilia were the FVL mutation (14/41, 34.1%), the prothrombin G20210A mutation (13/41, 31.7%), inherited protein S deficiency (10/41, 24.4%), and methylene tetrahydrofolate reductase (MTHFR) C677T mutation (6/41, 14.6%); whereas the major causes of secondary thrombophilia were surgery (334/418, 79.9%), malignant tumor (43/418, 10.3%), and pregnancy and perinatal period (17/418, 4.1%).