Pericardial Effusion and Tamponade as the Manifestation of Erdheim–Chester Disease

We hereby report the case of a 77-year-old man hospitalized due to pericardial effusion and tamponade. Upon investigating potential etiologies of the pericardial effusion, we diagnosed him with non-Langerhans cell histiocytosis, also known as Erdheim–Chester disease or polyostotic sclerosing histiocytosis, a rare histiocytic neoplasm. This case underscores the importance of considering less-common causes of pericardial effusion.