ABSTRACT
Inferior vena cava thrombosis (IVCT) is rare. Thrombophilia is one of the important risk factors. It is also uncommon for gene mutations in F9 gene to cause thrombosis but not hemorrhage. A 35-year-old male patient was admitted to our department with left lower limb swelling without an obvious cause for 1âday. Through contrast-enhanced computed tomography and color Doppler ultrasound, he was found to have lower extremity deep vein thrombosis, IVCT and pulmonary embolism. Through whole-exome sequencing analysis, he was found to carry a 925.7âkb duplication (chrX:137939698-138865419, hg19) encompassing ATP11C , SRD5A1P1 , MCF2 , FGF13 and F9 genes. This duplication of F9 gene was not detected in his parents. Other thrombophilic genes defects were not found. The factor IX activities of this patient, his father and mother were 194, 70 and 148, respectively. He was treated with catheter-directed thrombolysis, AngioJet-assisted pharmaco-mechanical thromboectomy and manual aspiration thromboectomy. Complete recanalization of left femoral, iliac veins and inferior vena cava was achieved. F9 gene duplication is a rare mutation, which can induce multiple venous thrombosis through increasing the activity level of factor IX in plasma. IVCT is a serious type of venous thrombosis. Personalized intervention treatment plans should be developed based on the different clinical characteristics of each case to achieve a higher benefit-risk ratio.