This lecture provides a comprehensive overview of Erdheim-Chester disease (ECD), a rare multisystemic clonal non-Langerhans histiocytosis with characteristic imaging manifestations across multiple organ systems. The lecture emphasizes that diagnosis depends on recognizing patterns of multisystem involvement rather than isolated organ findings, with radiologists playing a pivotal role in suggesting the diagnosis, guiding biopsy, staging disease extent, and monitoring treatment response. Particular attention is given to the hallmark imaging findings—including bilateral long-bone sclerosis, hairy kidneys, coated aorta, and right atrioventricular groove pseudotumor—as well as important differential diagnoses such as IgG4-related disease.

Learning Objectives

• Recognize the characteristic imaging manifestations of Erdheim-Chester disease across the skeletal, cardiovascular, renal, pulmonary, central nervous system, orbital, and endocrine systems, and identify the hallmark signs that should prompt consideration of the diagnosis.
• Apply a pattern-recognition approach to multisystem imaging by integrating findings from multiple organ systems rather than interpreting abnormalities in isolation, allowing earlier recognition of Erdheim-Chester disease.
• Differentiate Erdheim-Chester disease from important mimics, particularly IgG4-related disease and other causes of retroperitoneal fibrosis or multisystem inflammatory disease, by identifying distinguishing imaging features such as bilateral symmetric long-bone sclerosis.
• Understand the role of imaging in patient management, including selecting appropriate biopsy targets, assessing disease extent, evaluating cardiac and vascular involvement, and supporting molecular characterization that guides targeted therapy and prognosis.