S3654 Rash, Abdominal Pain, and the Clue in CBC: A Case of Recurrent Pancreatitis Revealing Hypereosinophilic Syndrome

Introduction: Hypereosinophilic syndrome (HES) is a rare group of disorders defined as an elevation in absolute eosinophil count (AEC) (>1.5 × 109/L on 2 or more occasions at least 4 weeks apart) in the absence of identifiable causes such as parasitic infection or hematologic malignancy, and eosinophil-associated organ damage. This report highlights the successful management of HES presenting as recurrent episodes of pancreatitis. Case Description/Methods: A 21-year-old man with ankylosing spondylitis, asthma, and Gilbert’s syndrome presented with history of recurrent abdominal pain for over 30 months. His first episode of pancreatitis occurred 24 months ago and has since experienced 6 such episodes. During these episodes he reported abdominal pain, generalized rashes, and had lipase levels ranging from 340-1120 U/L (upper normal limit 60 U/L). On imaging (computed tomography, endoscopic ultrasound, endoscopic retrograde cholangiopancreatography (ERCP), Magnetic resonance cholangiopancreatography (MRCP)) there was no evidence of acute or chronic pancreatitis. Labs revealed an AEC of 1.84 × 10⁹/L, with previous elevations of 2.02 × 10⁹/L and 1.73 × 10⁹/L noted on 2 occasions within the past year, each more than 4 weeks apart, along with markedly elevated IgE level (4440 IU/mL). Endoscopic biopsies revealed esophageal (35/HPF) and gastric (70/HPF) eosinophilia. Patient was started on Ivermectin based on a positive Strongyloides IgG test, but it yielded no benefit. On bone marrow biopsy hypereosinophilia (18%) was noted along with no findings suggestive of malignancy. Mepolizumab (anti-IL5) was initiated 4 months after presentation, leading to normalization of eosinophil counts, no recurrence of pancreatitis, and marked improvement in baseline abdominal symptoms. Discussion: HES is an extremely rare condition and is considered a diagnosis of exclusion. In this case, treatment was initiated only after comprehensive investigations ruled out other known causes of eosinophilia. The case highlights the value of clinical suspicion and the role of basic investigations such as complete blood count in identifying potential HES. Early recognition is crucial and can help reduce misdiagnosis in this rare but treatable condition.