Case Presentation: A healthy five-year-old girl was admitted from Ophthalmology Clinic for evaluation of bilateral anterior uveitis, fatigue and weight loss. History was notable for a cat scratch to the right eye one month prior which had prompted the referral to Ophthalmology Clinic. Patient also reported fatigue, night sweats, intermittent headache, poor oral intake, and a 4.5-kilogram weight loss over one month. On admission she was febrile to 39 degrees Celsius, heart rate was 80 beats per minute, blood pressure was 119/57 mmHg, respiratory rate was 24 breaths per minute, and she was fully saturated on ambient air. Exam was notable for a fatigued but non-toxic girl with photophobia, and diffuse abdominal tenderness to palpation without hepatosplenomegaly, rebound, or guarding. She had no nuchal rigidity, joint findings, lymphadenopathy, or rash, and a complete neurologic exam was normal. A comprehensive metabolic panel was unremarkable, and a complete blood count revealed a white blood cell count of 11.6 cells/uL, hemoglobin of 11.9 g/dL and platelets of 101 cells/uL. ESR was 53 mm/hr and CRP was 5.19 mg/dL. A chest radiograph and abdominal ultrasound were within normal limits. Repeat formal eye exam on hospital day two revealed new bilateral optic disc edema. A computed tomography scan of the head revealed extensive dural sinus venous thrombosis with vasogenic edema and 3mm midline shift. Subsequent computed tomography scans of the chest and abdomen revealed bilateral subsegmental pulmonary emboli, complete thrombosis of the right and middle hepatic veins and incomplete thrombosis of the portal and renal veins consistent with a diagnosis of thrombotic storm. The patient was transferred emergently to the intensive care unit and anticoagulated with a continuous infusion of intravenous heparin. A multidisciplinary evaluation revealed a normal hypercoagulability work-up including genetic testing and her clinical presentation was not consistent with a known hematologic, auto-immune or auto-inflammatory syndrome. She was transitioned to therapeutic enoxaparin and was initiated on immunomodulatory therapy with prednisone, azathioprine and infliximab for treatment of thrombotic storm with stabilization and of thrombus burden over three weeks.

Discussion: Thrombotic storm is an acute, extreme prothrombotic state characterize by multiple thrombotic events affecting diverse vascular beds over a short period of time (1). The etiology and pathophysiology are unknown, but it is felt to be likely secondary to an aberrant endothelial response to a prothrombotic stimulus. Affected patients are usually younger and present with two or more arterial or venous thromboemboli, often at unusual sites (i.e. cerebral venous sinuses and intraabdominal) (2). Anticoagulation with unfractionated heparin or a direct thrombin inhibitor is the mainstay of treatment and many patients have shown clinical response to immunomodulatory therapies including plasma exchange, corticosteroids, and rituximab.

Conclusions: Thrombotic storm is a rare condition with high morbidity and mortality that should be considered in pediatric patients presenting with unexplained venous thromboembolism. Hospitalists should be familiar with the clinical characteristics of thrombotic storm as the diagnosis requires a high level of clinical suspicion and appropriate diagnostic imaging studies to confirm the diagnosis. Early recognition and initiation of anticoagulation is imperative in improving clinical outcomes for patients.