Filiform Polyposis of the Terminal Ileum as the Initial Manifestation of Crohn’s Disease: A Case Report

BACKGROUND Filiform polyposis (FP) is a rare pseudopolyp associated with inflammatory bowel disease (IBD), characterized by elongated mucosal projections. It is found primarily in the colon and rectum, and presentation in the ileum is rare. Despite its benign nature, FP can mask underlying chronic intestinal inflammation. CASE REPORT A 52-year-old woman presented with loose stool but no other gastrointestinal symptoms. She was found to have a branched mucosal mass in the terminal ileum and diffuse ulcerations throughout the colorectum. Initial laboratory tests indicated anemia and elevated inflammatory markers. After 3 months of treatment with mesalazine and adjuvant drugs, the symptom of loose stool had improved, but the colonoscopy and imaging examination results show little change from the initial visit. Colonoscopy, imaging, and histopathology supported a diagnosis of Crohn's disease (CD). The ileal mass was identified as filiform polyposis. After multidisciplinary consultation, she was treated with Ustekinumab, leading to significant symptomatic and endoscopic improvement. The mass was subsequently resected via hybrid ESD and confirmed as an inflammatory polyp. CONCLUSIONS This case reveals that although a patient has no significant symptoms related to CD, FP located at the terminal ileum can initially manifest as CD, highlighting the need for through evaluation to detect underlying IBD. Multidisciplinary collaboration is essential for accurate diagnosis and management. FP can be the "tip of the iceberg" in hidden chronic intestinal inflammation, necessitating careful endoscopic and histologic assessment.