An Unusual Case of Disseminated Erdheim-Chester Disease.

Introduction: Erdheim-Chester disease (ECD) is a rare non-Langerhans histiocytic multisystem disorder, deriving from mononuclear phagocytic cells. It is notoriously challenging to diagnose. Here we present a case of a patient with multisystem ECD.

Case presentation: A 76-year-old female with a history of Hashimoto's thyroiditis who presented with persistent leukocytosis was found to have bilateral renal enlargement with a perinephric mass, a recurrent pericardial effusion, and bilateral pleural effusions. Following biopsies of several sites of involvement, a diagnosis of ECD was made.

Discussion: The existing literature on ECD is sparse, and no diagnostic criteria have been put forward due to widely differing presentations, although the most common is skeletal. Definitive diagnosis requires a tissue sample.

Conclusions: In presenting our clinical reasoning and approach, we hope to contribute to the existing body of literature on ECD, with the aim of ultimately having sufficient data to compile a diagnostic framework for other clinicians who encounter ECD.