A Case of Erdheim-Chester Disease with Omental Caking Initially Mistaken for a Malignancy

Introduction: Erdheim-Chester disease (ECD) is an uncommon non-Langerhans cell histiocytosis. Bilateral symmetric sclerosis of the long bones and possible multiorgan involvement are the main presentations of this disease. Histologically, lipid-laden foamy histiocytes are positive immunochemically for CD68 (occasionally for PS100) and negative for S100 and CD1a in ECD. Case Presentation: We describe the case of a 35-year-old man diagnosed with ECD with peritoneal and retroperitoneal infiltrations and bone involvement. The diagnosis of ECD was only confirmed after two years of non-specific abdominal pain, nausea, and weight loss. Primarily, the patient’s clinical symptoms and abdominal computed tomography (CT) findings, which indicated omental caking, peritoneal thickening, and perinephric soft tissue density, suggested an intra-abdominal malignancy. Finally, a peritoneal biopsy was carried out, which demonstrated xanthogranulomatous infiltrations from ECD. Further radiographic skeletal survey based on histopathological results showed symmetric osteosclerosis of the long bones. Conclusion: Although ECD, associated with peritoneal and retroperitoneal infiltrations, is an uncommon finding, it should be included in the differential diagnosis of patients with non-specific gastrointestinal manifestations, along with multiorgan involvement and typical radiological findings.