Beyond the Obvious Provoking Factor: May-Thurner Syndrome Presenting With Extensive Venous Thromboembolism in an 18-Year-Old Male

May-Thurner syndrome (MTS), also known as iliac vein compression syndrome or Cockett syndrome, is an anatomical vascular disorder characterized by chronic extrinsic compression of the left common iliac vein between the overlying right common iliac artery and the fifth lumbar vertebral body.Although MTS is a well-established cause of left-sided iliofemoral venous thrombosis, it is classically described in women between the second and fourth decades of life and remains underdiagnosed outside this population.We present the case of an otherwise healthy 18-year-old male student with no history of surgery, no prior medical comorbidities, recent hospitalizations, surgical procedures, lower-extremity trauma, or longdistance travel, and no personal or family history of thromboembolic disease.However, he presented with extensive left lower-extremity deep venous thrombosis extending into the inferior vena cava, accompanied by bilateral pulmonary emboli.Comprehensive evaluation revealed severe compression of the left common iliac vein consistent with MTS as the primary underlying etiology.