Kidney and inferior vena cava abnormalities with leg thrombosis (KILT) syndrome presenting as extensive iliofemoral deep vein thrombosis in a young patient.

Kidney and inferior vena cava abnormalities with leg thrombosis syndrome is a rare cause of extensive deep vein thrombosis (DVT) in young patients without evident provoking factors. We report a 19-year-old male patient presenting with severe right lower limb pain, swelling, and inability to bear weight after recovery from cardiac arrest due to long QT syndrome. A duplex ultrasound scan revealed extensive iliofemoral DVT, and contrast-enhanced computed tomography revealed the congenital absence of the inferior vena cava with extensive collateral circulation and right renal hypoplasia, confirming kidney and inferior vena cava abnormalities with leg thrombosis syndrome after the exclusion of inherited and autoimmune thrombophilia. The patient was treated with anticoagulation, catheter-directed thrombolysis, mechanical thrombectomy, and venous angioplasty, resulting in marked clinical improvement. This case indicates the importance of early cross-sectional imaging and individualized management in young patients with unprovoked extensive DVT.