Erdheim-Chester Disease Diagnosed by a Pericardial Fluid Cell Block Analysis.

Erdheim-Chester disease (ECD) is a rare histiocytic disorder that poses significant diagnostic challenges owing to its non-specific symptoms. We herein report the case of a 71-year-old woman with exertional dyspnea and bilateral edema who was initially suspected to have heart failure based on cardiomegaly and pericardial effusion. Pericardiocentesis with a cell block analysis revealed histiocytes that were positive for CD68 and negative for CD1a, thus increasing the likelihood of ECD. The bone biopsy results were consistent, thus leading to a diagnosis of ECD. This case highlights the diagnostic utility of a pericardial fluid cell block analysis, which offers a minimally invasive method to identify ECD in patients with significant pericardial effusion.