Working Diagnosis:
Chronic extensive deep venous thrombosis of the right iliac vein extending through the calf vein, presenting with post-thrombotic syndrome in the setting of lupus anticoagulant syndrome.

Treatment:
The patient was managed conservatively with compression therapy and a structured conditioning program. Following consultation with hematology, an interdisciplinary decision was made to not initiate systemic anticoagulation. There was a discussion regarding starting life-long anticoagulation due to an increased risk of stroke, myocardial infarction, and pulmonary embolism even in isolated lupus anticoagulant positivity. Per the hematologist, the data on isolated lupus anticoagulant positivity was not nuanced enough to make a definitive decision to empirically start anticoagulation. The patient, now an adult, and his parents decided to forego anticoagulation after several visits with the hematologist.

Outcome:
The patient resumed low-impact exercise with a protocol emphasizing gradual mechanical loading and specialized vascular rehabilitation. His symptoms improved with the consistent use of compression garments and targeted hydration strategies. However, he continues to report mild pain and swelling following strenuous exercise.

Author's Comments:
This case highlights a critical diagnostic pitfall in evaluating young athletes during the COVID-19 pandemic era. In young, healthy populations, acute unilateral lower extremity swelling is frequently misattributed to benign musculoskeletal conditions like hamstring strains or gastrocnemius tears, especially during telehealth visits where physical examination is limited. However, COVID-19 is a documented trigger for systemic immune dysregulation which can unmask or drive a chronic state of Antiphospholipid Syndrome (2, 5). While post-viral lupus anticoagulant positivity is often transient and resolves within 12 weeks, this patient represents a rare cohort where a persistent hypercoagulable state led to extensive, chronic deep venous thrombosis spanning from the iliac vein through the calf (5).
When a standard musculoskeletal injury fails to progress as expected, or when persistent swelling and superficial collateral veins develop, clinicians must maintain a high index of suspicion for deep vein thrombosis and subsequent post-thrombotic syndrome, even years after the initial viral illness (4). Early utilization of venous Doppler ultrasound is a low-risk, high-yield diagnostic step that can prevent permanent valvular damage, chronic morbidity, and delayed rehabilitation in athletes.

Editor's Comments:
Clinicians should consider initiating a work up for deep venous thrombosis and a hypercoaguable state with a clinical presentation of persistent leg pain and swelling from a prior injury or chronic soft tissue condition and a history of COVID-19. While the risk of a thrombotic condition is typically increased in the subacute window after COVID-19, it can be increased chronically in rare cases.

References:
1. Hampel L, Haase N, Klok FA, et al. Post COVID-19 Condition and the Risk of Venous Thromboembolism. JAMA Network Open. 2023;6(3):e231538. doi:10.1001/jamanetworkopen.2023.1538

2. Bikdeli B, Madhavan MV, Jimenez D, et al. COVID-19 and Thrombotic or Thromboembolic Disease: Implications for Prevention, Antithrombotic Therapy, and Follow-Up: JACC State-of-the-Art Review. Journal of the American College of Cardiology. 2020;75(23):2950-2973. doi:10.1016/j.jacc.2020.04.031

3.Whitworth H, Sartain SE, Kumar R, et al. Rate of thrombosis in children and adolescents hospitalized with COVID-19 or MIS-C. Blood. 2021;138(2):190-198. doi:10.1182/blood.2020010218

4. Klaassen I, Sari S, van Ommen H, et al. Incidence and risk factors for post-thrombotic syndrome in neonates and children in a single-center cohort study. Journal of Thrombosis and Haemostasis. 2025;23(1):181-189. doi:10.1016/j.jtha.2024.09.018

5.Hasan MN, Chowdhury FR, Islam KMK, Sami CA, Islam MT. Antiphospholipid Antibodies in Severe COVID-19: Frequency, Clinical Features, and 12-Week Follow-Up. Cureus. 2026 Jan 3;18(1):e100657. doi: 10.7759/cureus.100657. PMID: 41487320; PMCID: PMC12762132.

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