A rare case of unprovoked venous thromboembolism manifestation in a young patient with antithrombin Type IIB deficiency combined with inferior vena cava anomaly from Lithuania

SummaryHereditary antithrombin (AT) deficiency is an autosomal-dominant disorder predisposing to venous and arterial thrombosis. Homozygosity resulting in severe AT deficiency is not compatible with life, apart from homozygous mutations affecting the heparin-binding site representing the most severe thrombophilia. Patients and methods: A 12-year-old previously healthy boy of Romani origin presented with a swollen, painful left leg and fever. Imaging revealed signs of inferior vena cava (IVC) thrombosis, the presence of interrupted intrahepatic IVC with azygos continuation and bilateral iliofemoral thrombosis wit…