Bone mineral density and bone microarchitecture in a cohort of patients with Erdheim-Chester Disease

BACKGROUND: Erdheim-Chester Disease (ECD) is a rare type of non-Langerhans histiocytosis. Skeletal structures are affected in over 95% ECD patients. Due to the lack of proper imaging assessment tools, the alteration of bone microarchitecture in ECD has not been well studied. High-resolution peripheral quantitative computed tomography (HR-pQCT) is a newly developed assessment of bone mineral density and bone microarchitecture. METHODS: We performed a cross-sectional study with 13 patients diagnosed with ECD in Peking Union Medical College Hospital between October 2018 and June 2019. The diagnosis of ECD was based on typical pathological findings in the context of appropriate clinical and radiological manifestations. Bone geometry, volumetric bone mineral density and bone microarchitecture of those ECD patients were assessed using HR-pQCT at the non-dominant distal radius and distal tibia. Those HR-pQCT parameters were then compared to an ongoing population-based database of HR-pQCT for Mainland Chinese. RESULTS: As a result, remarkable heterogeneity of osteosclerosis in the HR-pQCT images was found in ECD patients, ranging from apparent normal structure, scattered thickening of trabecula, to homogenous consolidation. In terms of quantitative measurements, total volumetric BMD (383.50 mg/cm(3), 1.352 times of normal mean, p = 0.023) of the tibia differed significantly in ECD patients, due to the increased trabecular volumetric BMD (291 mg/cm(3), 2.058 times of normal mean, p = 0.003). The increased trabecular volumetric BMD of tibia was associated with remarkably increased number of trabecula (1.7/mm, 1.455 times of normal mean, p = 0.002) and increased thickness of trabecula (0.37 mm, 1.466 times of normal mean, p = 0.003). These differences could be due to the existence of dense bone interposed in the trabecula. CONCLUSION: This study is the first to assess the volumetric bone mineral density and bone microstructure with HR-pQCT in a cohort of ECD patients and indicated that the application of HR-pQCT may help to reveal the nature of bone lesions in the disease.