Case Description
The patient presented due to new onset chest pain and persistent left leg pain and swelling after a hyperextension injury of the knee 4 days prior forced him to be immobilized. He was tachycardic on presentation with otherwise normal vital signs. Physical examination was significant for left lower extremity swelling from knee to ankle with limited range of motion secondary to swelling and pain. Although he had erythematous skin changes on his ankle, he had palpable pulses and normal capillary refill. He had a normal cardiopulmonary examination. His known trauma, immobilization, and obese body mass index (34 kg/m2) were considered possible etiologies to provoke the thromboses, and his family history was unremarkable for thrombosis. Doppler ultrasonography showed extensive occlusive thrombosis of left femoral and popliteal veins. May-Thurner syndrome was ruled-out given the limited proximal extent of the left leg thrombus and venous anatomy. Chest computed tomography angiography demonstrated saddle PE with thrombus extending into the left and right pulmonary arteries (Fig. 1). Echocardiogram showed no evidence of right ventricular systolic failure or dilation, and brain natriuretic peptide and troponins were normal. He was hemodynamically stable and his PE was categorized as low-risk. No procedural interventions were indicated.
He was initially started on therapeutic anticoagulation with intravenous unfractionated heparin titrated to achieve anti-Xa level between 0.3-0.7 units/mL. He required oxygen support via nasal cannula but was weaned to room air within 48 hours of presentation. He was transitioned to enoxaparin at pediatric therapeutic starting dose of 1 mg/kg and titrated to achieve an anti-Xa level between 0.5-1 units/mL. Upon discharge, he still had swelling and pain of the lower extremity but was able to ambulate on crutches.
Despite his known preceding trauma, immobility, and obesity, he underwent laboratory evaluations for underlying thrombophilia due to the degree of thrombosis on presentation. Results were significant for heterozygous mutations of both FVL and PT-G20210A, positive anti-beta 2 glycoprotein I (aβ2GPI) IgG antibody, and lupus anticoagulant (LA; positive Staclot, negative diluted Russell viper venom time); his aβ2GPI IgM and anti-cardiolipin (aCL) IgM/IgG antibodies were all negative. He was discharged home on therapeutic enoxaparin due to concern for reduced efficacy of direct oral anticoagulants in treatment of patients with APS. Repeat testing at 3 months re-demonstrated the same findings for his antiphospholipid antibody profile, which was consistent with a diagnosis of APS based on the Sapporo criteria.Repeat Doppler ultrasonography at 3 months demonstrated improvement but residual non-occlusive thrombosis of left femoral and popliteal veins and therapeutic enoxaparin was continued.