ERDHEIM‐Chester Disease: Two Fatal Cases With Unusual Presentations

We present two fatal cases of Erdheim‐Chester disease (ECD) with unusual presentations: one featuring predominant gastrointestinal involvement with steatorrhea, nodular gastroduodenitis, and extensive visceral infiltration, and another with constrictive pericarditis and pachypleuritis. Both cases displayed characteristic imaging findings including the “hairy kidney” sign, “coated aorta” sign, symmetric long bone osteosclerosis, and diffuse FDG‐PET avidity in bone marrow and serosal surfaces. Histopathology confirmed xanthogranulomatous infiltration with foamy histiocytes and Touton giant cells, with immunohistochemistry showing CD68‐positive, CD163‐positive, CD1a‐negative, and S100‐negative cells lacking Birbeck granules, consistent with non‐Langerhans cell histiocytosis. These atypical organ manifestations, when accompanied by characteristic radiological signs, should prompt consideration of ECD in the differential diagnosis of multisystem inflammatory disorders.