Case Presentation: A 36-year-old previously healthy female presented to the emergency department with one-day history of decreased visual acuity and spontaneous contractions of her right fourth and fifth digits. Review of systems was positive for a month history of dyspnea on exertion, hives, mild edema of ankles, wrists, hands, lips and eyes, as well as recent dyspepsia and diarrhea. She had no known allergies and no significant family history. She had no active substance use or recent travel. Vital signs were within normal limits. Physical exam was significant for impaired visual acuity, decreased grip strength of right hand with involuntary flexion of the fourth and fifth fingers, and significant bilateral lower leg non-pitting edema.CBC showed leukocytosis of 25,400 cells/L with absolute eosinophil count of 17,800 cells/L. High-Sensitivity Troponin-I was elevated 5,171.8 ng/L without EKG or echocardiography findings of ischemia. Lower extremity ultrasound revealed partially occlusive thrombi in bilateral proximal posterior tibial and peroneal veins. Brain MRI showed multiple bilateral supratentorial and cerebellar infarcts. This constellation of symptoms raised suspicion for a hypereosinophilic syndrome. Infectious, rheumatologic, atopic, and neoplastic diagnostics were pursued. This workup, including bone marrow biopsy, was negative for underlying etiology. A diagnosis of idiopathic HES was made.

Discussion: Hypereosinophilic syndromes (HES) are a group of rare disorders that are characterized by hypereosinophilia (absolute eosinophil count >1,500 cells/L) with eosinophil-mediated organ damage not explained by another causative factor. Multiple clinical variants of HES exist, with myeloproliferative and lymphocytic subtypes being most common. The syndrome usually demonstrates dermatologic, pulmonic, and gastrointestinal involvement; rarely, such as in this case, it may also affect the cardiovascular and nervous systems. The widespread thrombotic events and ischemic ulnar neuropathy of this presentation can be attributed to eosinophilic damage, theorized to involve pro-inflammatory cytokine production, reactive oxygen species generation and endothelial damage promoting the clotting cascade.

Conclusions: The patient was treated with high-dose intravenous steroids along with therapeutic anticoagulation, aspirin, and atorvastatin. Eosinophil count normalized, and the patient’s visual acuity and ulnar neuropathy improved. The patient was discharged on prednisone and hydroxyurea with a plan for follow up with hematology and allergy.