Pediatric thromboembolism: a national survey in Japan

Thromboembolism is being detected at increasing rates in pediatric tertiary care hospitals. The incidence of pediatric thrombophilia differs across countries, and is unknown in Japan. We sent a survey to 520 pediatric department heads and 629 specialists, requesting details on patients who developed symptomatic thromboembolism between 2006 and 2010. Of 280 eligible cases, congenital thrombophilia and other conditions were reported. Congenital thrombophilia (n = 54, 19.3 %) comprised defects in protein C (27), protein S (9), and antithrombin (7). None had mutations in factor V Leiden or prothrombin G20210A, both of which are frequent in Caucasians. Non-congenital causes of thrombophilia included congenital heart disease, the use of central venous catheters, nephrotic syndrome, antiphospholipid syndrome, and malignancy with or without use of L-asparaginase. Patients with congenital thrombophilia developed thromboembolism at a significantly younger age (median 1.0 vs. 5.0 years, p = 0.014), had a higher frequency of consanguinity (35.2 vs. 1.8 %, p < 0.001) and post-thrombotic syndromes (29.6 vs. 13.3 %, p = 0.007) than those who did not. Thromboembolism in children with congenital thrombophilia recurred more frequently (50.0 vs. 13.7 %, p < 0.001) and was associated with more sequelae (61.1 vs. 37.2 %, p = 0.009) than in children without congenital thrombophilia. This nationwide survey provides the first comprehensive study of Japanese children with symptomatic thromboembolism. Significant recurrence and sequelae require optimized standards.