INTRODUCTION: Hypereosinophilic Syndrome (HES) is a rare disorder most commonly diagnosed in patients 20-50 years of age. It is defined as a persistent absolute eosinophil count greater than 1500 cells/microL and/or pathologic confirmation of tissue hypereosinophilia, as well as evidence of end-organ dysfunction. Prior to making a diagnosis, allergic, rheumatologic, infectious, and neoplastic etiologies should be excluded. CASE DESCRIPTION/METHODS: This is the case of an 87 -year-old male with past medical history of malaria treated with chloroquine who presented with altered mental status, dry cough and ascites de novo. Associated symptoms included unintentional weight loss of 10-15 lbs and intermittent episodes of non- bloody, watery diarrhea. He denied history of alcohol or drug use. Physical exam was remarkable for a distended abdomen with a positive fluid wave and pitting edema +1 in the lower extremities bilaterally. Labs showed a platelet count of 53,000, hypoalbuminemia (1.9 g/dl), increasing creatinine (2.1 mg/dl), alkaline phosphatase of 444 u/l, total bilirubin of 2.8 mg/dl with indirect predominance, AST of 59 u/l, ALT of 55 u/l, and eosinophilia of 72% (absolute eosinophil count of 6,048). Abdominal sonogram with doppler failed to show obstructive pathology and no evidence of hepatic vein thrombosis. Paracentesis showed absence of malignant cells, SAAG >1.1, 0.79 g/dl of protein and abundant eosinophils. Hepatitis, Iron Saturation levels, AMA, ASMA, Schistosoma and Strongyloides workup were negative. Hematology oncology service was consulted for bone marrow biopsy to asses for myeloid and lymphoid disorders. Results showed a hypercellular bone marrow with marked eosinophilia and 50% nucleated cells but C-KIT, PGFR Alpha, PGFRB, BCR/ABL, JAK 2 and TCR were all negative. A diagnosis of Hypereosinophilic Syndrome with suspected eosinophilic liver infiltration was made and the patient was started on prednisone therapy. All prior described multisystemic symptoms resolved. Eosinophilia, thrombocytopenia and all liver enzymes normalized within 24-48 hours after initiation of therapy. Ascites also resolved for which diuretic therapy was discontinued. DISCUSSION: This case is interesting as HES has an incidence of 0.36 per 100,000, and hepatic involvement accounts solely for an estimated 30% of patients. This serves to illustrate that HES should form part of the differential diagnosis when hepatic involvement and eosinophilia are concerned as prompt evaluation and treatment can lead to rapid resolution.