Deep vein thrombosis in a 14-year-old boy with a combination of May–Thurner syndrome, protein S deficiency and lupus anticoagulant: a case report

BACKGROUND: Here, we present the first reported case of a child presenting with unprovoked deep vein thrombosis (DVT) due to the unique combination of May-Thurner syndrome, protein S deficiency and lupus anticoagulant. Of interest to the clinician and scientific reader alike is that this one-of-a-kind interplay between mechanical obstruction and hypercoagulability caused a very extensive blood clot which extended from the left popliteal to the femoral and iliac veins. A 12-month course of warfarin with a target INR value of 2.5 was used to treat the DVT which would be of use to note for any future clinicians treating children presenting with extensive DVTs and multiple pro-thrombotic risk factors. CASE PRESENTATION: A 14-year-old Asian (Han Chinese) boy presented to the children's assessment unit with a 4-day history of left-sided groin pain radiating to the left knee. On examination his left thigh was swollen. Initial blood tests showed no clotting abnormalities and a normal platelet count. An ultrasound doppler of the lower limb veins was performed which showed an extensive thrombus involving the left popliteal, femoral, and iliac veins. An MRI of the abdomen and pelvis demonstrated that the left common iliac vein was narrowed by the left common iliac artery thereby confirming May-Thurner syndrome. He was started on enoxaparin bridging therapy to rivaroxaban initially. Further blood tests were positive for lupus anticoagulant. He was also found to be protein S deficient. After further discussions with haematological services a 12-month course of warfarin was indicated due to rivaroxaban being contraindicated in patients with antiphospholipid syndrome (APS). Our patient was suspected of having APS but to confirm, a second blood test had to be sent at least 12 weeks after the first. Warfarin was therefore started as we could not wait 12 weeks to confirm or refute a diagnosis of APS. The patient eventually tested negative for APS. After 12 months of treatment with warfarin, a repeat ultrasound doppler was performed which showed that the thrombus had almost entirely resolved with good flow in all the previously affected veins. He was subsequently started on a lower dose of rivaroxaban as maintenance therapy. CONCLUSIONS: Based on our literature search this is the first patient to be reported as having this unique combination of May-Thurner syndrome, protein S deficiency and testing positive for lupus anticoagulant. This case demonstrated that despite the child having such an extensive thrombus and presenting with multiple risk factors for thrombosis, that a 12-month course of warfarin with a target INR of 2.5 was sufficient in resolving his symptoms and facilitated the dissolution of the clot. This case also demonstrated the importance of considering APS as a risk factor for his clot as having this condition would contraindicate the use of DOACs. Testing negative for lupus anticoagulant on his repeat blood test, a reduced dose course of rivaroxaban (at 10 mg instead of 20 mg once daily) was indicated and was successful in ensuring that there was no recurrence of DVT with no reports of major or minor bleeds nor of any thromboembolic events occurring.