Recurrent Leg Deep Vein Thrombosis in a Female with Atypical Right-Sided Variant of May Thurner Syndrome and Factor V Leiden Mutation

Abstract

I ntroduction: May-Thurner syndrome (MTS) is a condition in which the right common iliac artery presses on the left common iliac vein, causing it to narrow over time. Right-sided MTS is a rare event. We present this unique case of recurrent right leg deep vein thrombosis in a female with atypical right sided variant of MTS and Factor V Leiden mutation. Case Presentation: A 34-year-old lady with with no signficiant past medical history presented to the hospital with right lower leg edema, tingling, and discolouration. She was taking oral contraceptive pills. Vitals were unremarkable. Doppler studies revealed right lower extremity deep vein thrombosis in the right external iliac vein, common iliac vein and common femoral vein. She was started on an intravenous heparin drip and subsequently had a thrombectomy procedure. She was subsequently discharged home on apixaban anticoagulation. We opted to request a hypercoagulable and vasculitis workup in light of the extensive thrombosis, despite the OCP risk factor, and discovered a heterozygous Factor V Leiden mutation. She returned to the hospital 2 days later with worsening right leg pain. Repeat Doppler studies demonstrated acute right femoral and popliteal deep vein thrombosis. CT angiography of abdomen and pelvis revealed significant right femoral vein DVT that extends into the External iliac vein, common iliac vein, and IVC to at least slightly below renal vein level. Invasive Radiology was consulted and she had a venogram and intravascular ultrasound (IVUS) which showed high-grade right common iliac vein and IVC stenosis (>90%) at L4 superior endplate. Iliac stenting and angioplasty improved iliac and inferior IVC diameters. Patient also underwent thrombectomy & IVC filter placement. The diagnostic venography revealed a popliteal-to-proximal femoral vein rethrombosis. This was treated with tissue plasminogen activator (TPA) by 8 French power pulse AngioJet and a mechanical thrombectomy. This resulted in partial clearing of the common femoral vein with persistent narrowing and thrombosis of the popliteal vein. TPA was infused at 1 mg/hour with a 5 French McNamara lysis catheter over the popliteal region.Patient transferred to ICU for overnight intravenous thrombolysis. The patient was then re-initiated on the heparin drip and then bridged to therapeutic warfarin. Discussion: MTS is a phenomenon commonly described as an acquired stenosis of the left common iliac vein secondary to compression by the right common iliac artery 1. It has been associated with genetic clotting factor abnormalities, repeated pregnancies, postpartum, contraceptive pills, prolonged immobilization, scoliosis, anti-phospholipid syndrome, COVID-19, and recurrent DVT 2. In patients with left lower-limb DVT, the incidence of MTS is about 20-50%. Right lower limb DVT in patients with right sided variant of MTS is rare. Right lower limb DVT with right sided variant of MTS with co-existing Factor V Leiden mutation is even rarer. Ultrasound imaging typically cannot detect the high pelvic abnormalities seen in MTS. Contrast venography, MRI, or IVUS are needed to diagnose MTS 4. As was the case in our patient, venography should be done to evaluate stenosis and iliac vein compression hemodynamics after thrombus removal. Treatment of MTS depends on the presentation, severity of symptoms, and whether the patient has developed DVT. Conservative treatment such as compression stockings can be used for patients who are asymptomatic or have mild symptoms. For patients with moderate symptoms or DVT, endovascular treatment with stenting is recommended 5. Conclusion: This is a very atypical presentation of MTS variation affecting the right lower extremity with limited description in the literature. To our knowledge, this is the first case presentation of right sided MTS resulting in a DVT in a patient with factor V Leiden mutation. MTS is a potentially treatable and often-overlooked pathology. In the era of expanded endovascular management of MTS, recognition of this disease entity is essential for early diagnosis and treatment.