Venous thromboembolism in children and adolescents

which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. There have been growing concerns about venous throm-boembolism (VTE), especially in Western counties where the incidence is greater than Asian counties. showing significantly lower incidence of VTE in children and adolescents in comparison to adults [1]. Although the incidence of VTE is remarkably lower in children compared to adults, pediatric VTE is also gaining increased awareness because severe VTE may lead to serious morbidity and even death in pediatric patients as well. It has been demonstrated that pediatric VTE is an increasingly common complication among hospitalized children, now occurring in 42–58/10,000 pediatric admissions [2, 3]; representing roughly a 10-fold increase over the original Canadian estimates from the early 1990s [4]. Of note, the majority of pediatric VTE occur in the tertiary care hospitals, where more intensive medical interventions with increased awareness and recognition can be provided [5]. Regarding the lower incidence of pediatric VTE, researchers have suggested that children have protective mechanisms: e.g. physiologic deficiency of coagulation factors leading to reduced capacity to generate thrombin; increased capacity of 2-macroglobulin to inhibit thrombin; enhanced antithrombotic potential of the vessel wall, and not yet being exposed to acquired thrombotic predictors such as smoking or antiphospholipid antibodies [6]. VTE including deep vein thrombosis (DVT) and pulmonary embolism (PE) usually develops as a secondary complication of underlying clinical conditions such as venous catheterization, malignancy, infection/sepsis, congenital heart disease, trauma/surgery, and inherited or acquired thrombophilia, all of which act as risk factors for VTE in children and adolescents. Among these, the most common risk factor for VTE in pediatric patients is the venous catheterization [5, 6]. During intensive or supportive care of pediatric patients who require total parenteral nutrition, chemotherapy, or antibiotic administration, more than half of the DVTs in children and more than 80% of neonates occur in the upper extremity veins secondary to venous catheterization [6]. The impact of inherited thrombophilia on the pediatric VTE remains inconclusive mainly due to lack of statistical power [7]. However, VTE is a multifactorial disease, in which multiple heritable and environmental risk factors affect the overall disease risk, we may have to consider the involvement of inherited thrombophilia that includes deficiencies of antithrombin, protein C and protein S, and mutations of factor V Leiden (G1691A) and prothrombin (factor II G20210A), as 'additional' risk factors for VTE in children and …