INTRODUCTION: Hypereosinophilic syndrome (HES) is a rare disorder of eosinophil accumulation that can affect any organ leading to heterogeneous presentations. Diagnosis is often delayed due to nonspecific symptoms. The authors present a rare case of hypereosinophilia with recurrent gastrointestinal (GI) symptoms. CASE DESCRIPTION/METHODS: A 45-year-old Vietnamese female with history of asthma initially noted four months of dyspnea, lower extremity edema, abdominal distension, and transient rash. She then presented to the ER with persistent abdominal pain, nausea, vomiting, and diarrhea. Serology was notable for WBC 11.1 × 103/uL with 36.8% eosinophils, albumin 2.3 g/dL, total bilirubin 2.9 mg/dL. CT was significant for moderate hepatomegaly, abdominal ascites, diffuse intestinal wall thickening. Peritoneal fluid had 44% eosinophils, SAAG of 0.9 g/dL. ESR, CRP, and serum immune-electrophoresis were elevated, but autoimmune and stool studies for malabsorption and infections were negative. Ascites, hypoalbuminemia and hyperbilirubinemia suggested infiltrative hepatic disease, but liver chemistries were normal and she declined liver biopsy for further evaluation. Endoscopic exam found erosions, erythema and friability in the entire duodenum and terminal ileum. Random biopsies showed focal eosinophilic crypt abscess. Treatment with prednisone was delayed due to suspicion of lymphatic filariasis (filaria antibody 5.94, positive IgG4). Unfortunately, patient was lost to follow up and was re-admitted a few months later for continued abdominal symptoms and fluid overload. Incidental observation of “jellied” blood prompted evaluation of serum viscosity, notably elevated at 15.5. Despite plasma exchange, she developed unilateral paralysis with diffuse multifocal arterial and venous thrombi. Further work up with bone marrow biopsy, cytogenetics with fluorescent in-situ hybridization were negative for alternative causes of eosinophilia. DISCUSSION: Over 10 months, the patient developed multisystem idiopathic HES with components of atypical eosinophilic granulomatosis with polyangiitis. Serology improved with corticosteroid and rituxan. She ultimately made a full recovery on prednisone. This case describes the multifarious presentations of eosinophil deposition within the GI tract. Given its nonspecific presentation and potential to progress to debilitating systemic manifestations, a high index of suspicion for HES is advised when hypereosinophilia is observed peripherally and at other sites.Figure 1.: CT abdomen and pelvis. Patient had mild to moderate hepatomegaly, mild ascites, diffuse wall thickening involving small and large bowel loops which may be related to infectious/inflammatory process, mildly enlarged retroperitoneal mesenteric lymph node that are reactive.Figure 2.: Endoscopic image of duodenal bulb. Endoscopies showed diffuse moderate inflammation with edema, erythema, erosions, and friability.Figure 3.: Random colon biopsy with H&E stain, 400x A single eosinophilic crypt abscess can be seen. Note surrounding eosinophilia in the lamina propria (arrows).