Objective  To summarize the features of ^99mTc-methylene diphosphonate (MDP) whole-body bone scintigraphy (WBBS) in Erdheim-Chester disease (ECD) patients and to provide insights for clinical diagnosis and treatment.

  Methods  Retrospective analysis was performed in ECD patients with bone lesion who underwent ^99mTc-MDP WBBS at Peking Union Medical College Hospital from January 2015 to December 2022.The bone involvement sites and characteristic features in^99mTc-MDP WBBS were summarized, and the correlation between bone lesion scores and bone metabolic biomarkers was analyzed.

  Results  A total of 44ECD patients with bone involvement were included in the study.According to the ^99mTc-MDP WBBS, the most commonly affected sites were the bones of the extremities (100%, 44/44), skull and maxillofacial bones (84.1%, 37/44), and appendicular bones (65.9%, 29/44), while involvement of the ribs and sternum (38.6%, 17/44) and spine (29.5%, 13/44) were less frequent.Bilateral and symmetric change of the lesions was an important feature of ^99mTc-MDP WBBS in ECD.The proportion of patients with bilateral and symmetric bone lesions in the extremities, maxillofacial area, and clavicle was relatively high, particularly in the lower extremities (100%).In extremity bone lesions, there was mostly joint involvement of diaphysis and metaphysis, and 81.8%(36/44) patients demonstrated the typical scintigraphic characteristic: bilateral and symmetrical increased uptake in the distal femur and proximal tibia.The maxillofacial lesions mainly presented with focal uptake increase in the region of the paranasal sinuses, with or without diffuse increased uptake in the mandible-Lincoln sign (61.1%, 22/36).Spearman correlation analysis revealed that the bone metabolic biomarkers such as blood calcium, blood phosphate, alkaline phosphatase, and parathyroid hormone were not linearly correlated with bone lesion scores (all P>0.05).

  Conclusions  ECD can cause multiple bone lesions, with involvement typically observed in the extremities, particularly in the lower extremities.Lesions in the skull and maxillofacial area are also frequently observed.Bilateral and symmetric uptake increase in the distal femur and proximal tibia is the most pathognomonic manifestation of ^99mTc-MDP WBBS, providing valuable information for diagnosing and differentiating ECD.