More Than Just Stool: Hypereosinophilic Syndrome Presenting as Persistent Diarrhea in a Patient With Ulcerative Colitis.

We highlight a case of non-infectious diarrhea that progressed despite supportive care, prompting further workup. A 50-year-old man presented with 1 week of voluminous diarrhea, nausea, emesis, and abdominal pain. His history included ulcerative colitis, primary sclerosing cholangitis, Clostridioides difficile treated via total colectomy with ileoanal pouch, treated disseminated Mycobacterium avium complex, and international travel. On physical exam he had normal vital signs, diffuse abdominal tenderness without peritoneal signs, and a rash. Lab work revealed leukocytosis with eosinophilia, hyponatremia, and elevated creatinine. Lactate, inflammatory markers, stool studies, and computed tomography of his abdomen were normal. Tissue biopsies of the duodenum, ileum, and rectal pouch collected during colonoscopy and push enteroscopy revealed prominent mucosal eosinophilia, confirming the diagnosis of hypereosinophilic syndrome (HES). Treatment with steroids led to significant improvement in all symptoms and blood eosinophilia. This case highlights the importance of aggressive workup of diarrhea with peripheral eosinophilia, especially in patients with ulcerative colitis: waiting 6 months to confirm the diagnosis via blood work would delay treatment. Notably, infection with Strongyloides stercoralis was ruled out in this case prior to treatment. This is an important step in the workup and management of HES to prevent progression of Strongyloidiasis.