Abstract 112: When Cell Blood Count Matter, Hypereosinophilic Syndrome a Rare Cause of Ischemic Strokes
Authors: Kaur Gunjanpreet , Rodriguez Wilson , Singh Divya , Cadmus Rachel , Esechie Aimalohi , Edgell Randall 
Published: March 2024

Introduction
Hypereosinophilic syndrome (HES) is a rare hematological disorder defined by persistently elevated blood eosinophil count (>1500/μL), associated with evidence of organ damage. It can occasionally present primarily with neurological conditions such as ischemic strokes, encephalopathy, or sensory neuropathy. Driving hypothesized mechanisms are hypercoagulability owing to eosinophil‐related endothelial damage or cardioembolism. We present an unusual case of ischemic strokes due to HES in the setting of Fip1‐like 1‐platelet‐derived growth factor receptor alpha (FIP1L1‐PDGFRA) mutation.

Methods
The patient was identified in routine clinical practice.

Results
38 year‐old‐male with no significant medical history who was transferred to our institution for blurred vision, and dizziness. His initial National Institutes of Health Stroke Scale was 3 for bilateral leg weakness. The neurological exam was pertinent for paresis in his left arm and legs. Magnetic resonance imaging (MRI) of the brain demonstrated multiple acute infarcts in bilateral cortical and subcortical structures as shown in Figure 1. Computed tomography angiography (CTA) of the brain and neck did not show significant stenosis or occlusion. During admission, transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) did not reveal any source for cardioembolism. Subsequently, he developed hyperactive delirium requiring anti‐psychotics. He was worked up for any infectious etiology because he continued to have a leukocytosis with an eosinophil count as high as 49%. Doppler of lower extremities showed deep vein thrombosis in the left femoral vein. Hematology evaluated the patient and, after performing a bone marrow biopsy, he was diagnosed with primary Hypereosinophilic syndrome (HES) in the setting of FIP1L1‐PDGFRA mutation. He was started on high‐dose methylprednisolone, hydroxyurea and later switched to Imatinib. A cardiac MRI was performed which was negative for eosinophilic myocarditis. The patient's mental status improved significantly after starting Imatinib and his anti‐psychotics were discontinued. In regards to secondary prevention, vascular neurology wanted antiplatelet monotherapy, however, the patient was started on Apixaban to treat his DVT. He was followed up in the stroke clinic 2 months after discharge, his modified Rankin score (mRS) was 1. Aspirin was recommended for secondary stroke prevention once hematology considers it safe to discontinue apixaban.

Conclusion
This case encourages the consideration of HES in patients with low cardiovascular risk factors who have infarcts following a cardioembolic or watershed pattern in brain imaging. Going back to the basics and reviewing simple laboratory tests like cell blood count can be the initial clue for diagnosis. Early recognition is crucial as immunosuppression is the most important treatment in the acute phase. While imatinib is the treatment of choice for FIP1L1‐PDGFRA mutation HES, patients continued to be at risk of stroke recurrence despite having normal eosinophil count as described by Rohmer et al.