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Risk of thrombosis with anomalies of the inferior vena cava and factor V Leiden

To the Editor: Congenital anomalies of the inferior vena cava (IVC) are a rare vascular defect [1,2]. The diagnosis is made in children when the defect is associated with another congenital anomaly or incidentally during abdominal surgery or radiological procedures [3,4]. The prevalence of IVC anomalies is about half percent [5]. Venous thromboembolic events (VTE) develop less frequently in children than in adults (0.07–0.14 per 10,000 children) [6]. VTEs in children and adolescents are usually secondary complications of a primary illness or therapy. Only 2–4% of childhood VTEs are spontaneous and most associated with one or more prothrombotic risk factors. We describe a case of a child with absence of the IVC (aIVC) and factor V Leiden (FVL) mutation, both of which represent prothrombotic risks. A 17-year-old, non-smoker, male presented to the emergency department of our medical center with complaints of chest pain, shortness of breath, and left leg pain. He had been diagnosed with varicose veins at age 11 years and anomalous venous return with aIVC at age 12. Family history was remarkable for multiple strokes on the maternal side and FVL mutation in both a maternal aunt and uncle. CT scan of the chest with intravenous contrast was negative for pulmonary embolism. Doppler ultrasound of legs found a left femoral and left popliteal deep vein thrombosis (DVT) with large collaterals. He was admitted to the pediatric intensive care unit and treated with a combination of thrombolysis (48 h) and low molecular weight heparin for 6 months with no evidence of thrombus after 3 months of therapy. Evaluation for thrombophilia protein C, protein S, antithrombin, prothrombin mutation, homocysteine levels, lipoprotein-a levels, and lupus-like anti-coagulant screen, disclosed heterozygosity for FVL as the only abnormality. Literature review disclosed eight reported cases with the association of VTE, aIVC and FVL, 3 were children. The pediatric cases are limited to 3 teenagers reported by Molina et al. [4], Parma et al. [7], and Chee et al. [5]. There is an additional report of a neonate with the combination of VTE, aIVC and FVL, but no details of the case are available [8]. Absence of IVC itself contributes to the risk of VTE [1,9]. The etiology of aIVC is unclear. Possible hypotheses are embryonic dysontogenesis that affects separate segments of the IVC, intrauterine thrombosis, or umbilical vein complications postpartum [1]. FVL confers a 7-fold increase in the risk for VTE in heterozygotes, and an 80-fold increase in homozygotes [4]. In children with spontaneous VTE FVL Is the most frequent associated prothrombotic factor in North America and Europe. The absence of IVC represents a risk for VTE due to venous stasis. The association of aIVC and FVL or another prothrombotic disorder may further increase the risk of VTE. Conversely, the increased risk for VTE associated with hereditary prothrombotic states like FVL may have predisposed the fetus or embryo to thrombotic events that may have resulted in the aIVC. Given the paucity of data, no firm conclusion can be reached, but these associations deserve further study.