Background <p>Eosinophilic fasciitis is a rare connective tissue disorder characterized by fascial inflammation and eosinophil infiltration. Thromboembolic complications in eosinophilic fasciitis are uncommon and poorly understood. We report a case that highlights the limitations of conventional anticoagulation in preventing eosinophil-mediated thrombosis.</p> Case presentation <p>A 60-year-old Chinese man presented with a 10-day history of progressive bilateral lower extremity swelling and pain. Laboratory investigations revealed severe hypereosinophilia and imaging revealed left lower-extremity deep vein thrombosis complicated by acute compartment syndrome. Despite therapeutic enoxaparin anticoagulation with documented hypocoagulable state on thromboelastography, the patient developed bilateral lacunar infarctions on day 7. Bone marrow aspiration excluded hematological malignancies, and fascial biopsy confirmed eosinophilic fasciitis. Following glucocorticoid therapy initiation, eosinophil levels normalized with complete resolution of symptoms. No recurrence of thrombotic events was observed during one-year follow-up.</p> Conclusion <p>This case highlights that eosinophilic fasciitis-associated hypereosinophilia can induce a prothrombotic state resistant to conventional anticoagulation, likely through eosinophil granule protein-mediated mechanisms. Early recognition and prompt glucocorticoid therapy, rather than anticoagulation alone, may be critical for preventing life-threatening thromboembolic complications in eosinophilic fasciitis. This report adds to the limited literature on thrombotic manifestations of eosinophilic fasciitis and underscores the need for heightened clinical vigilance and a shift in therapeutic paradigm toward early immunosuppression.</p>